Vaccination with Aleutian mink disease parvovirus (AMDV) capsid proteins enhances disease, while vaccination with the major non-structural AMDV protein causes partial protection from disease

Vaccination studies were performed with partially purified recombinant AMDV VP1/2 capsids as well as with the major AMDV non-structural protein (NS1). All vaccine constructs induced an antibody response, but did not prevent infection upon challenge with AMDV. The severity of Aleutian disease (AD) was judged by the serum gammaglobulin level, the quantity of peripheral blood CD8 lymphocytes, antibody titers to VP1/2 and NS1 proteins and mink death rates. The VP1/2 vaccine constructs enhanced the disease process with drastic death rates for the vaccinated mink. On the contrary, the NS1 vaccine constructs resulted in milder AD than seen in the non-vaccinated mink.     

Left ventricular wall thickening does occur in elite power athletes with or without anabolic steroid Use

Monoclonal antibodies (mAbs) against bovine leukocyte antigens specific for T cells (CD2, CD4, CD8 and gammadelta receptor) and B cells (surface IgM) were used in samples from one week and one-, three- and seven-month-old goats to study the evolution of lymphocyte subsets by flow cytometry in peripheral blood and the lymphoid organs: thymus, jejunal (JPP) and ileal (IPP) Peyer's patches, spleen and mesenteric lymph nodes. An increase in the values of alpha/beta receptor T cells with age was recorded whereas the gammadelta receptor T cells fell in number. In peripheral blood and in all tissues, except IPP the values for B cells (sIgM+) were low. The CD4+ and CD8+ cells predominated in JPP while B cells were the most important subpopulation in IPP. In the spleen, as in JPP, the CD4/CD8 ratio was less than one and the gammadelta T cells values were high. In mesenteric lymph nodes, CD8+ and B(sIgM) cells predominated in the youngest animals.     

Use of an automated fluorescent microsphere method to measure regional blood flow in the fetal lamb

OBJECTIVE: To investigate the source of the expanded blood CD8+ subsets during an acute primary simian immunodeficiency virus (SIV) infection of macaques and the potential role of these cells in disease progression. DESIGN AND METHODS: The primary CD8+ lymphocytosis, which occurs at 1-2 weeks following infection with SIVsmm/PBj-14, was examined in rhesus and cynomolgus macaques. Extensive subset analysis of the expanded blood CD8+ cell pool in a rhesus macaque was compared phenotypically with those in thymus, lymph nodes, spleen, ileum and lung washouts obtained at necropsy during blood lymphocytosis. The influence of the primary CD8+ cells expansion on disease progression was assessed at days 175-679 post-infection in long-term PBj-14 survivors staged according to immunological, virological and histopathological changes in their lymphoid organs. RESULT: The very rapid and transient blood lymphocytosis following infection consisted of two distinct CD45RA(low), CD8+ and CD28-, lymphocyte function-associated antigen (LFA)-1(high), CD45RA(high), CD8+ populations. These populations were present in low levels in thymus, lymph and spleen but were highly represented in mucosal tissues, such as long washout, in which CD28- LFA-1(high) CD45RA(high) CD8+ cells comprised 86% of CD8+ cells, and gut, which was predominantly CD45RA(low) CD28- CD8+ cells. A comparison of progressor and non-progressor PBj-14-infected rhesus and cynomolgus macaques also indicated that the existence or magnitude of a blood CD8+ lymphocytosis during the acute phase of infection did not by itself appear to influence or be predictive of disease progression. CONCLUSION: The marked blood CD8+ lymphocytosis observed during acute SIV infection did not result from expansion of virus-specific precursors in peripheral lymph node and did not appear to influence the rate of disease progression. The findings provide a novel explanation for the primary CD8+ cell lymphocytosis and invoke a mechanism whereby virus-induced cytokine/chemokine production in mucosal sites initiate the transient migration of a pre-existing CD8+ population into the blood from compartments such as lung and gut. Such results suggest that the magnitude of lymphocytosis may depend on the level of viral replication in mucosal tissues and the presence of other infections, for example, cytomegalovirus.     

Differences in the kinetics of T cell accumulations in C3H/HeN (Bcg-resistant) and C57BL/6 (Bcg-susceptible) mice infected with Mycobacterium paratuberculosis

The accumulation of various T cell subsets in Bcg-susceptible (C57BL/6) and- resistant (C3H/HeN) strains of mice were compared following an intraperitoneal infection with Mycobacterium paratuberculosis. Groups of mice from both strains were killed at 3, 5, 10, 15, 30, and 150 days after infection and lymphocytes were harvested from the peritoneal exudate cells (PEC), spleen, intestinal epithelial lymphocytes (IEL), lamina propria lymphocytes (LPL), Peyer's patches, and mesenteric lymph node (MLN) and labelled with monoclonal antibodies to CD3, CD4, CD8, gamma delta TCR, CD25, and CD44 for flow cytometric analysis. Uninfected C3H/HeN mice had higher proportions of CD4+ cells in the spleen, MLN, LPL, IEL, and Peyer's patches, while uninfected C57BL/6 mice had higher proportions of CD8+ and/or gamma delta T cells. Significant increases in accumulation of CD8+ and gamma delta T cells were detected in the peritoneum and other tissues in both strains of mice after infection. Higher CD4/CD8 ratios were observed in most lymphoid tissues of C3H/HeN mice, while increased proportions of CD8+ and/or gamma delta T cells were present in C57BL/6 mice. These results indicate that significant differences in T cell profiles exist between these two strains of mice, both inherently and in response to infection with M. paratuberculosis. Innately lower levels of CD4+ cells and/or higher percentages of CD8+ and gamma delta T cells may play a role in the increased suspectibility of C57BL/6 mice to infection with M. paratuberculosis.     

Prenatal ontogeny of lymphocyte subpopulations in pigs

Although porcine lymphocytes have been classified into numerous subpopulations in postnatal animals, little is known about the ontogeny of these complex cell subsets. Using double- and triple-colour flow cytometry (FCM), we investigated the surface phenotype of fetal lymphoid cells in the thymus, cord blood, spleen and mesenteric lymph nodes at different stages of gestation. It was found that the major lymphocyte subpopulations started to appear at the beginning of the second third of the gestation period, with B cells being the earliest lymphocyte subpopulation to appear in the periphery. The T-cell receptor (TCR) gamma delta+ cells were the earliest detectable T-cell subset, developing first in the thymus and subsequently arriving in the periphery. Later in ontogeny, however, the number of TCRalpha beta+ lymphocytes rapidly increased, becoming the predominant T cells both in the thymus and in the periphery. Cells with the phenotype of adult natural killer cells were also identified in pig fetuses, though their nature and functional roles remain to be investigated. In addition, CD2 was expressed on most B cells whilst very few CD4+ TCRalpha beta+ cells or CD2+ TCRgamma delta+ cells expressed CD8, suggesting that the expression of CD2 and CD8 may reflect the functional status of the cells in postnatal animals. Taken together, this study has provided a systematic analysis of fetal porcine lymphocyte subpopulations and may provide the base for studies to establish the physiological roles of these lymphocyte subsets.     

Rhesus thymic/liver xenografts in severe combined immunodeficient mice: immunologic reconstitution and intrathymic infection with simian immunodeficiency virus

By serving as host recipients of xenografts from both humans and animals, severe combined immunodeficient (SCID) mice have become valuable to many laboratories interested in examining the pathophysiology of different diseases. To gain insight into the usefulness of the SCID mutation in retrovirus research, rhesus monkey fetal hematolymphoid tissues (liver and thymus) were used to construct a SCID-rhesus chimeric mouse (SCID-rh) and were engrafted in the renal capsule. The size and maturation of the thymic engrafts were monitored grossly, histologically, and immunologically. SCID mice were tolerant to rhesus tissues, and thymic engrafts contained thymocytes at different stages of maturation and differentiation that had morphologic features similar to age-matched rhesus thymus. Mature single positive CD2+, CD4+, and CD8+ T lymphocytes that were phenotypically similar to rhesus T lymphocytes were present at low levels (2% to 5%) in the peripheral blood and at moderately higher levels (7% to 15%) in the spleens of SCID-rh mice obtained between 12 and 15 weeks after thymus/liver engraftment. Within 3 weeks after engraftment, > 85% of the thymocytes in the thymic engrafts were immature double positive CD4+CD8+ T cells. The highest number of positive cells were seen in thymic engrafts obtained at 12 to 18 weeks. During these weeks, > 90% of the cells were double positive (CD2+CD4+, CD2+CD8+, and CD4+CD8+). After infection of the engrafted thymus tissue with simian immonodeficiency virus (SIVmac239), PCR analysis revealed successful viral infection of engrafts at 2 and 4 weeks after infection. No significant histopathologic and flow cytometric changes were observed in the thymic engrafts at 2 and 4 weeks after infection. An unrelated lesion of thymic lymphomas involving the SCID host thymus was seen in 12% of the mice. The data presented herein suggest that the SCID-rh is a valuable model for specific studies related to thymus-retrovirus interaction and that it could be used for further studies. The results are discussed in relation to current knowledge of thymus involvement during simian and human immunodeficiency virus infection.     

Local intestinal immune responses to infections with Trichinella spiralis. Real-time, continuous assay of cytokines in the intestinal (afferent) and efferent thoracic duct lymph of rats

Levels of IL-4, IL-5, TNF-alpha, and IFN-gamma were quantitated in the intestinal (afferent) and efferent thoracic duct lymph of rats during the course (0 to 289 h) of an infection with Trichinella spiralis. Intestinal lymph was collected by cannulating thoracic ducts of mesenteric lymphadenectomized animals. These studies showed that cytokines typical of a Th2 type (IL-4 and IL-5) and a Th1 type (IFN-gamma) were simultaneously detected in the intestinal lymph during the first 8 days after infection. Worm expulsion (day 11 to 12) was associated with increased levels of IL-4 and IL-5 in the intestinal lymph. IL-5 levels rose as early as 15 to 20 h and remained elevated throughout the infection. IL-4 activity appeared in intestinal lymph 60 h after infection and reached peak levels during worm expulsion. Despite the predominantly Th2 nature of cytokine response, IFN-gamma levels showed several cycles of high and low production during the course of infection. A comparison of cytokine levels between intestinal and efferent lymph values showed no significant differences in IL-4 or IL-5 levels suggesting no contribution by the mesenteric node to efferent lymph. However, IFN-gamma and TNF-alpha levels were lower in efferent lymph compared with intestinal lymph suggesting mesenteric node consumption. Adoptive transfer experiments showed that protective CD4+CD45RC- cells primed the gut for a more rapid TH2-type response that was faster than in a primary infection. In contrast, adoptive transfer of CD4+CD45RC+ cells primed the gut for a more rapid Th1-type(IFN-gamma) response. These studies demonstrate a novel method for measuring real-time changes in cytokine levels in the gut during the course of an active infection.     

Mucosal immunodeficiency in HIV/SIV infection

The gastrointestinal tract is one of the major target organs for secondary infections and malignancies in HIV infection in humans indicating disturbed local immunologic defense mechanisms. Immunohistology and flow cytometric studies have demonstrated a more pronounced loss of CD4+ T cells in the intestinal mucosa compared to the peripheral blood in humans infected with HIV. In parallel, activated CD8+ T cells in the lamina propria are increased in this compartment. In SIV-infected nonhuman primates a very early loss of CD4+ T cells in the intestinal mucosa compared to the peripheral blood occurs already at 2 weeks after infection. Depletion and functional impairment of mucosal CD4+ T lymphocytes with consecutive altered cytokine secretion in HIV/SIV infection may explain the breakdown of the mucosal immune barrier leading to secondary opportunistic or nonopportunistic infections and secondary malignancies. In addition, due to the interrelation between the mucosal immune system and epithelium, these changes might be responsible for the partial small intestinal mucosal atrophy and maturational defects in enterocytes observed in HIV-infected patients.     

Selective expansion of activated V delta 4+ cells during experimental infection of mice with Leishmania major

Previous work from this laboratory has revealed that infection of mice with Leishmania major leads to an expansion of gamma delta+ T cells in the spleen. Further examination of the gamma delta+ T cells expanding in infected mice has shown that the majority of these cells in the spleen, lymph nodes, blood and liver expressed the V delta 4 gene segment. Cell cycle analysis, using propidium iodide incorporation, demonstrated that while only 1% of alpha beta+ T cells in the spleen were in either S + G2/M phase, up to 10% of the gamma delta+ T cells were in cycling phase 8 weeks after infection. Comparison of the state of activation of the two populations in different organs after infection, confirmed that gamma delta+ T cells are actively dividing in lymph nodes, liver and blood, but not in the thymus or among intraepithelial lymphocytes. Examination of the expression of different activation markers on the surface of gamma delta+ T cells in the spleen of both normal and chronically infected BALB/c mice by FACS analysis, revealed increased expression of LFA-1, CD25, CD44, 4F2, CD28 and the heat-stable antigen, whereas Thy-1 and CD5 decreased. Collectively, these results suggest an oligoclonal expansion and activation of gamma delta+ T cells in response to L. major infection.     

Activation and 'deletion' of self-reactive mature and immature T cells during ontogeny of Mls-1a mice: implications for neonatal tolerance induction

We assessed the kinetics of V beta 6+ T cell elimination in the lymph nodes and thymus during Mls-1a mouse ontogeny. Our results suggest that induction of tolerance to Mls-1a antigens involves mechanisms other than clonal deletion of immature T cells in the thymus. Mature CD4+CD8- (CD4SP) T cells were affected by Mls-1a antigens earlier than immature thymocyte populations. Up to 2 weeks after birth, reduced frequencies of V beta 6+ T cells were detected only in CD4SP cells from the thymus and lymph nodes, and generation of CD4SP cells in the thymus was blocked at least 1 week earlier than that of their CD4+CD8loTCRhi immature precursors. The number of V beta 6+CD4SP T cells increased during the first 2 weeks of life and remained constant thereafter. We thus found no evidence of deletion of mature V beta 6+CD4SP T cells, as the reduced frequencies in adult mice can be attributed to the dilution of previously generated cells in lymphoid organs of growing mice, which increase in cellularity after birth. V beta 6+CD4+ T cells were activated in vivo shortly after birth, as shown by a selective increase in IL-2 receptor alpha chain expression in the thymus and lymph nodes from day 0 to day 2 after birth. It is therefore likely that endogenous expression of Mls-1a antigen shortly after birth activates V beta 6+CD4SP T cells and renders them anergic. This process of tolerance induction may precede the clonal deletion of immature T cells in the thymus, described in the adult mouse.     

Influence of detergents on the function of cloned potassium channels

The human thymus is a lymphoepithelial organ in which T cells develop during fetal life. After maturation and selection in the fetal thymic microenvironment, T cells emigrate to peripheral lymphoid tissues such as the spleen, gut, and lymph nodes, and establish the peripheral T cell repertoire. Although the thymus has enormous regenerative capacity during fetal development, the regenerative capacity of the human postnatal thymus decreases over time. With the advent of intensive chemotherapy regimens for a variety of cancer syndromes, and the discovery that infection with the Human Immunodeficiency Virus (HIV) leads to severe loss of CD4+ T cells, has come the need to understand the role of the human thymus in reconstitution of the immune system in adults. During a recent study of the thymus in HIV infection, we observed many CD8+ T cells in AIDS thymuses that had markers consistent with those of mature effector cytotoxic T cells usually found in peripheral immune tissues, and noted these CD8+ effector T cells were predominately located in a thymic zone termed the thymic perivascular space. This article reviews our own work on the thymus in HIV-1 infection, and discusses the work of others that, taken together, suggest that the thymus contains peripheral immune cell components not only in the setting of HIV infection, but also in myasthenia gravis, as well as throughout normal life during the process of thymus involution. Thus, the human thymus can be thought of as a chimeric organ comprised of both central and peripheral lymphoid tissues. These observations have led us to postulate that the thymic epithelial atrophy and decrease in thymopoiesis that occurs in myasthenia gravis, HIV-1 infection, and thymic involution may in part derive from cytokines or other factors produced by peripheral immune cells within the thymic perivascular space.     

Early recovery of CD4+ T lymphocytes in children on highly active antiretroviral therapy. Dutch study group for children with HIV infections

INTRODUCTION: Regeneration of CD4+ T lymphocytes has been shown to be thymus-dependent in bone marrow transplant recipients and after intensive chemotherapy. The rate of CD4+ T cell regeneration is correlated positively with enlargement of the thymus, as shown on radiographs, and higher rates of CD4+ T lymphocyte regeneration were observed in children as compared with adults, consistent with thymic function diminishing with age. We hypothesized that in HIV infected patients CD4+ T cell recovery during highly active antiretroviral therapy (HAART) may also be thymus dependent. Therefore, repopulation of naive (CD45RA+), memory (CD45RO+) and total CD4+ T lymphocytes and total CD8+ T lymphocytes in peripheral blood was assessed in 13 HIV infected children during the initial 3 months of HAART. RESULTS: Significantly higher recovery rates of naive, memory and total CD4+ T cells were observed in children below the age of 3 years as compared with older children. Kinetics of total CD8+ T cells showed no relation to age. Moreover, recovery rates of naive CD4+ T cells in patients below 3 years of age were 10-40 fold higher as compared with previously reported naive CD4+ T cell recovery rates in adults on HAART. CONCLUSIONS: High recovery rates of naive, memory and total CD4+ T cells can be achieved in children below 3 years of age. Changes in CD8 counts did not correlate with age. These results indicate that regeneration of CD4+ T cells during HAART may be a thymus-dependent process.     

Abnormal thymocyte subset distribution and differential reduction of CD4+ and CD8+ T cell subsets during peripheral maturation in diabetes-prone BioBreeding rats

In this study we quantified CD8+ and CD4+ T cells in T lymphocytopenic BB rats as compared with control rats at given stages along the maturational pathway from immature thymocytes to mature peripheral T cells. Our results show that BB rats exhibit abnormal thymocyte subset distribution. Numbers of mature TCRhigh/CD4-8+ thymocytes, and also their TCRhigh/CD4+8+ precursors were decreased, as were levels of CD8 expression on all thymocyte subsets investigated. By analogy with mouse thymocyte development, these findings suggest a decreased efficiency for positive selection of CD8 precursors in BB rats. Furthermore, as related to the number of available mature TCRhigh single positive thymocytes, numbers of CD4+ and CD8+ T cells most recently migrated from the thymus were severely decreased in BB blood, indicating either reduced thymic output or rapid cell death after migration. Subsequently, in peripheral blood and cervical lymph nodes, a 95% decrease of CD8+ and a 50 to 80% decrease of CD4+ T cells were demonstrated upon maturation from recent thymic migrants to mature peripheral T cells, leaving the BB rat with a severely reduced T cell population, consisting of CD4+ T cells and a minute population of CD8+ T cells. The vast majority of the latter was found to have an immature peripheral phenotype. Possible consequences of our findings for the generation of autoreactive CD8+ T cells are discussed.     

Expression of growth hormone receptors in murine lymphoid cells analyzed by flow cytofluorometry

We have analyzed the expression of GH receptors (GHR) in murine lymphoid organs using flow cytofluorometry with biotinylated bovine GH and specific fluorescein isothiocyanate-labeled monoclonal antibodies defining distinct lymphoid cell populations. GHR were widely expressed in al murine hematopoietic tissues and in fetuses, newborns, and 3- and 7-week-old animals. In the bone marrow, all hematopoietic lineages expressed variable levels of GH receptors, whereas in the thymus, this expression was mainly seen in CD4-, CD8-, CD4+CD8+, and CD8+ subpopulations. At the periphery, 50% of splenocytes and peripheral blood lymphocytes and 20% of lymph node cells were GHR positive, with a wider receptor expression on B cells and macrophages (approximately 50%) than on T cells (approximately 20%), where the labeling was seen on both CD4+ and CD8+ cell subsets. Interestingly, the proportion of GHR-bearing CD4+ and CD8+ splenocytes significantly increased after T cell activation with Concanavalin A or anti-CD3. Finally, we demonstrated that all peripheral T cells expressing GHR also expressed PRL receptors. Our study provides a molecular basis to study the factors controlling GHR expression and to better understand the influence of GH in the regulation of immune function.     

CD8 dimer usage on alpha beta and gama delta T lymphocytes from equine lymphoid tissues

Eight murine monoclonal antibodies (mAb) were used to identify the equine CD8 alpha or CD8 beta chains and to define the expression of these chains on lymphocytes from various lymphoid tissues. CD8 alpha was a 39 kDa protein and CD8 beta was a 32 kDa protein. Both chains were expressed on most of the CD8+ T lymphocytes in the peripheral blood, spleen, thymus, mesenteric lymph nodes and ileal intraepithelial lymphocytes (IEL), however, in each lymphoid compartment a percentage of lymphocytes expressed only the CD8 alpha chain. The largest percentage of CD8 alpha alpha expressing T lymphocytes was 37.7% of the IELs. Purified T lymphocytes from the ileum expressing CD8 alpha beta co-expressed the alpha beta T cell receptor (TCR). In contrast, purified CD8+ T lymphocytes from the PBMC co-expressed either the alpha beta or gamma delta TCR by RT-PCR. Use of pooled anti-CD8 alpha mAb of the murine IgG2a isotype and rabbit complement resulted in lysis of the entire CD8 expressing population in peripheral blood mononuclear cells (PBMC). These results indicated that CD8 dimer usage by equine T lymphocytes is similar to other species and that the mAb described can be further used to separate equine CD8+ T lymphocyte subsets from the lymphoid tissues to define their function in protection against viral and other infections.     

Recent thymic emigrants in the rat express a unique antigenic phenotype and undergo post-thymic maturation in peripheral lymphoid tissues

Studies of the functional properties and developmental potentials of immediate post-thymic cells have been hampered by the lack of reliable markers with which to distinguish recent thymic emigrants (RTE) from the bulk of peripheral T cells. In the present study, the intrathymic FITC-labeling technique was used in concert with three-color flow-cytometric analysis to identify, phenotypically characterize, and study the short term fate of RTE in normal rats. The results indicated that between 3 and 4% of total T cells in lymph node and spleen of 5- to 8-wk-old rats had been released from the thymus within the preceding 24 h. Unlike the bulk of the peripheral T cells, which had a Thy1-, CD45RC+, and/or RT6+ phenotype, these RTE were Thy1+, CD45RC-, and RT6-. Furthermore, two discrete subsets of RTE were defined: a major subset (approximately 95%) of CD4+ or 8+ (single positive), TCR-alpha beta hi T cells that resembled medullary thymocytes; and a minor subset (approximately 5%) of CD4+ and 8+ (double positive), TCR-alpha beta low T cells that resembled cortical thymocytes. The following evidence suggested that most if not all Thy1+ T cells in young adult rats are RTE and their immediate descendants: 1) thymectomy (but not sham thymectomy) selectively depleted Thy1+ T cells from lymph node within 3 to 7 days, even in adrenalectomized rats; 2) most FITC-labeled RTE differentiated into Thy1-, CD45RC+, RT6+ T cells within 7 days of release from the thymus; 3) transitional phenotypes of Thy1+ T cells, including Thy1low, CD45RC+, and RT6+, were observed in normal, as well as in intrathymic, FITC-injected rats; 4) most T cells in neonatal rats were Thy1+ and RT6-, whereas their descendants were Thy1- and RT6+. These experiments demonstrate that most RTE in normal rats are phenotypically (and presumably developmentally) immature at the time of release from the thymus, and progressively acquire the phenotypic attributes of more mature T cells post-thymically. These unique phenotypic attributes should expedite the isolation of RTE and their immediate descendants for definitive studies of their developmental and functional properties.     

Human immunodeficiency virus infection of the human thymus and disruption of the thymic microenvironment in the SCID-hu mouse

Infection with the human immunodeficiency virus (HIV) results in immunosuppression and depletion of circulating CD4+ T cells. Since the thymus is the primary organ in which T cells mature it is of interest to examine the effects of HIV infection in this tissue. HIV infection has been demonstrated in the thymuses of infected individuals and thymocytes have been previously demonstrated to be susceptible to HIV infection both in vivo, using the SCID-hu mouse, and in vitro. The present study sought to determine which subsets of thymocytes were infected in the SCID-hu mouse model and to evaluate HIV-related alterations in the thymic microenvironment. Using two different primary HIV isolates, infection was found in CD4+/CD8+ double positive thymocytes as well as in both the CD4+ and CD8+ single positive subsets of thymocytes. The kinetics of infection and resulting viral burden differed among the three thymocyte subsets and depended on which HIV isolate was used for infection. Thymic epithelial (TE) cells were also shown to endocytose virus and to often contain copious amounts of viral RNA in the cytoplasm by in situ hybridization, although productive infection of these cells could not be definitively shown. Furthermore, degenerating TE cells were observed even without detection of HIV in the degenerating cells. Two striking morphologic patterns of infection were seen, involving either predominantly thymocyte infection and depletion, or TE cell involvement with detectable cytoplasmic viral RNA and/or TE cell toxicity. Thus, a variety of cells in the human thymus is susceptible to HIV infection, and infection with HIV results in a marked disruption of the thymic microenvironment leading to depletion of thymocytes and degeneration of TE cells.     

Immunity to porcine rubulavirus infection in adult swine

The immune response against the porcine rubulavirus was analyzed in experimentally infected adult pigs. High titers of virus neutralizing and hemagglutinating inhibitory antibodies were identified in infected animals. The antibody specificity was directed towards HN, M, and NP rubula virion proteins; immunodominance of HN proteins was demonstrated. Peripheral blood mononuclear cells from infected, but not from non-infected pigs proliferated in vitro in response to virus antigenic stimuli, showing a bell-shaped plot with the highest peak at 5 weeks post-infection. Virus-induced lymphoblasts expressed CD4+ CD8+ phenotype, whereas lectin-induced lymphoblasts were mainly identified as CD4+ CD8- cells. Phenotype analysis of freshly prepared PBMC revealed increased number of both monocytes (PoM1+) and total T lymphocytes (CD2+) early during infection, with reduced values of B lymphocytes at 4 weeks post-infection. Decrease in CD4+ CD8- blood cells was observed at 3 weeks post-infection, whereas both CD4- CD8+ and CD4+ CD8+ cells increased 1 and 4 weeks post-infection, respectively. This work discusses the relevance of CD4+ CD8+ T cells in the control of porcine rubulavirus infection.     

Analysis of splenic and thymic lymphocyte subpopulations in chickens infected with Salmonella enteritidis

Lymphocytes expressing CD3, CD4, CD8, pan lymphocyte, IgA, IgG and IgM cell surface antigens were assessed by in the spleen and thymus of chickens following infection with Salmonella enteritidis using flow cytometric analysis. At 6 days post primary infection and 2 days post secondary infection with S. enteritidis, the percentages of IgA+ and IgM+ lymphocytes in the spleen were significantly increased (P < 0.05). At 2 days post secondary infection with S. enteritidis, the percentage of CD4+ T lymphocyte in the spleen and CD8+ T lymphocyte percentage in the thymus were significantly increased (P < 0.05). These results indicate that S. enteritidis infection induces changes in the spleen and thymus that reflect the dynamics of the host protective immune response.