Acquired resistance but not innate resistance to Mycobacterium bovis bacillus Calmette-Guérin is compromised by interleukin-12 ablation

Interleukin-12 (IL-12) is one of the first cytokines produced by macrophages, key mediators of innate resistance, during the host's immune response to infections. Therefore, in this study we propose that IL-12 has an important role in the early phase of the immune response to Mycobacterium bovis BCG. IL-12 has been shown to enhance the maturation of protective Th1 cells and gamma interferon (IFN-gamma) production during mycobacterial infection. Therefore, it may play a crucial role during the immune phase of infection as well. To examine the role of IL-12 in both the innate and the immune phase of infection, we compared BCG-resistant mice, B10.A (Bcgr), to the susceptible congenic strain B10.A (Bcgs) following administration of a blocking monoclonal antibody to IL-12 (10F6). Anti-IL-12-treated susceptible animals exhibited a two- to threefold increase in spleen CFU by day 21. In contrast, anti-IL-12 treatment had little or no effect on the response of the genetically resistant animals to infection. The B10.A (Bcgr) but not the B10.A (Bcgs) mice had an increase in IFN-gamma mRNA relative to baseline levels as early as day 1 of infection irrespective of anti-IL-12 treatment. By day 14, B10.A (Bcgr) mice showed a decrease in IFN-gamma mRNA while the B10.A (Bcgs) mice showed a significant increase in IFN-gamma mRNA levels. Thus, during BCG infection, the B10.A (Bcgr) mice mount an early IFN-gamma response against BCG whereas the B10.A (Bcgs) mice have a delayed IFN-gamma response correlating with their genetic permissiveness expressed as an increased mycobacterial load by day 21. Overall, our data demonstrate that the inherent resistance of B10.A (Bcgr) mice to mycobacteria does not depend on optimal levels of IL-12 to maintain effective control of the bacteria, whereas IL-12 is important for the susceptible animals' response to BCG during the peak of infection.     

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.     

Dietary calcium modulates Mycobacterium paratuberculosis infection in beige mice

A 6-month study was conducted to evaluate the effects of feeding different levels of dietary calcium (Ca) on the persistence of Mycobacterium paratuberculosis infection using a mouse model. Beige mice, averaging 8 weeks of age, were randomly assigned to one of the following dietary treatments: 1) 0.02% Ca, 2) 0.15% Ca, 3) 0.45% Ca, and 4) 1.0% Ca. Mice were infected intraperitoneally with 10(8) CFU viable M. paratuberculosis for 1, 3, and 6 month periods. Plasma Ca levels was unaffected by dietary Ca (x = 7.3 mg/dl). Plasma levels of 1,25(OH)2D3 was elevated significantly in 0.02% and 0.15% Ca groups compared to other treatments at the end of each period, with the highest levels observed for 0.02% Ca mice and intermediate values for 0.15% Ca mice. One month after infection, numbers of viable M. paratuberculosis cultured from the spleen were significantly reduced for 0.15% Ca mice, whereas the number of bacteria isolated from the liver and mesenteric lymph node (MLN) were higher for the 0.02% Ca group. There were no differences in bacterial numbers in the ileum although they tended to be higher for the 0.02% Ca group. Three months after infection, bacterial numbers in the spleen, ileum, and MLN did not differ across treatments, however, significantly lower numbers were found in the liver of 1.0% Ca mice. Reduced bacterial counts were also observed in the liver of 0.15%. 0.45%, and 1.0% Ca mice after a 6-month infection period compared to the 0.02% Ca group, with the lowest numbers isolated from the 1.0% Ca mice. Numbers of viable bacteria cultured from the ileum and MLN after 6 months of infection were also significantly reduced in 1.0% Ca mice. These results suggest that Ca metabolism is an important modulator of M. paratuberculosis infection.     

Establishment of Bcgr congenic mice and their susceptibility/resistance to mycobacterial infection

Bcg congenic mice were developed by using C57BL/6 and DBA/2 strains of mice as progenitors. They were obtained by introgressively backcrossing the Bcgr marker of DBA/2 onto C57BL/6. After twenty successive backcrossings, the heterozygous resistant mice were mated with each other to obtain homozygous mice as the Bcgr congenic mice. The results of immunogenic and genetic markers coupled with those of an mixed lymphocyte reaction, all confirmed that the newly developed mice were highly congenic. These congenic mice were found to be resistant to in vivo infections by Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium bovis BCG.     

Low calcium diet and 1,25-dihydroxyvitamin D(3) infusion modulate immune responses during Mycobacterium paratuberculosis infection in beige mice

A 12-month study was conducted to evaluate the effects of feeding a low calcium (Ca) diet or 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3) infusion on the persistence of Mycobacterium paratuberculosis infection using a mouse model. Male beige mice 6-8 weeks of age were assigned to one of the following treatments: (1) non-infected, (2) infected,(3) non-infected/1,25(OH)(2)D(3), (4) infected/1,25(OH)(2)D(3), and (5) infected/low Ca (0.15 percent) diet. Infected mice were inoculated intravenously with live M. paratuberculosis. At 1, 6 and 12 months postinfection, mice in Treatments 3 and 4 were implanted subcutaneously with mini-osmotic pumps to deliver 1,25(OH)(2)D(3). Infusion with 1,25(OH)(2)D(3) exacerbated M. paratuberculosis infection in most tissues at all time points. Mice infused with 1,25(OH)(2)D(3) had higher bacterial counts in spleen, liver, and ileum compared with control infected mice after 1 month of infection. In contrast, feeding a low Ca diet reduced the number of viable organisms cultured from the liver and ileum of infected mice. Plasma Ca and 1,25(OH)(2)D(3) were increased in mice infused with 1,25(OH)(2)D(3) at all time points but values for low Ca mice were not different than for non-infused mice. Splenocyte production of TNF, IL-1 and IL-6 was higher for mice fed the low Ca diet compared with control infected mice after 1 month of infection. Inducible IL-6 activity remained higher for this treatment at 6 months postinfection. These results suggest that feeding a low Ca diet to mice chronically infected with M. paratuberculosis appears to enhance their ability to clear the infection in a manner distinct from any effect of 1,25(OH)2D3.     

Reconstitution of C.B-17 scid mice with BALB/c T cells initiates a T helper type-1 response and renders them capable of healing Leishmania major infection

C.B-17 scid mice, which were found to be very susceptible to infection with Leishmania major, were reconstituted with various doses of T cells, T plus B cells or unfractionated spleen cells from nonhealer BALB/c mice. All reconstitution protocols, except for the transfer of very high numbers of BALB/c spleen cells, led to a spontaneously healing infection and resistance to reinfection, rather than the lethal, nonhealing infection typical of BALB/c mice. These healing responses were associated with a strong T helper 1 (Th1)-like response characterized by delayed-type hypersensitivity (DTH) responsiveness, but no elevation of serum IgE, and by the production of high levels of interferon-gamma (IFN-gamma), but no interleukin-4 (IL-4) by lymph node and spleen cells after restimulation with antigen in vitro. The development of this Th1 response from BALB/c Th cells requires IFN-gamma during the initial infection period. Treatment of scid mice with a single injection of neutralizing anti-IFN-gamma antibody prior to infection and reconstitution prevented healing and permitted the development of a Th-2 like response as indicated by elevated serum IgE, but no DTH, and by the production of IL-4, but very little IFN-gamma, after antigen stimulation in vitro. As few as 10(4) transferred T cells led to a Th1-like response, suggesting that the IFN-gamma is of host rather than donor origin. The transfer of very high numbers (7.5 x 10(7)) of BALB/c spleen cells overcame the effects of the IFN-gamma and led to the nonhealing infection and cytokine pattern characteristic of BALB/c mice. The enrichment or depletion of B cells from the transferred T cells had no measurable effect upon the development of a healing response in reconstituted scid mice.     

Significant contribution of spleen cells in mediating the lethal effects of endotoxin in vivo

Two closely related, histocompatible mouse strains that have marked differences in both in vitro and in vivo responses to endotoxin were used to evaluate the contribution of lymphoid cells to the lethal effect of endotoxin. C3H/HeJ mice are endotoxin resistant, whereas C3H/HeN mice are endotoxin sensitive. In vitro spleen cell mitogenic responses to endotoxin were similar in untreated mice and in mice that received sublethal irradiation (450 R) followed by reconstitution with autologous spleen cells. Reconstitution with spleen cells from the related strain produced chimeric animals with spleen cell mitogenic activity like that of the donor strain. When chimeric animals were subjected to a lethal challenge of endotoxin, their response was markedly altered by the transferred lymphoid cells. C3H/HeJ animals reconstituted with C3H/HeN cells became more endotoxin sensitive, whereas C3H/HeJ cells became more endotoxin resistant. These results indicate that spleen cells play a significant, detrimental role in endotoxin-induced lethality.     

On the key role of secondary lymphoid organs in antiviral immune responses studied in alymphoplastic (aly/aly) and spleenless (Hox11(-)/-) mutant mice

The role of the spleen and of other organized secondary lymphoid organs for the induction of protective antiviral immune responses was evaluated in orphan homeobox gene 11 knockout mice (Hox11(-/-)) lacking the spleen, and in homozygous alymphoplastic mutant mice (aly/aly) possessing a structurally altered spleen but lacking lymph nodes and Peyer's patches. Absence of the spleen had no major effects on the immune response, other than delaying the antibody response by 1-2 d. In aly/aly mice, the thymus-independent IgM response against vesicular stomatitis virus (VSV) was delayed and reduced, whereas the T-dependent switch to the protective IgG was absent. Therefore, aly/aly mice were highly susceptible to VSV infection. Since aly/aly spleen cells yielded neutralizing IgM and IgG after adoptive transfer into recipients with normally structured secondary lymphoid organs, these data suggest that the structural defect was mainly responsible for inefficient T-B cooperation. Although aly/aly mice generated detectable, but reduced, CTL responses after infection with vaccinia virus (VV) and lymphocytic choriomeningitis virus (LCMV), the elimination of these viruses was either delayed (VV) or virtually impossible (LCMV); irrespective of the dose or the route of infection, aly/aly mice developed life-long LCMV persistence. These results document the critical role of organized secondary lymphoid organs in the induction of naive T and B cells. These structures also provide the basis for cooperative interactions between antigen-presenting cells, T cells, and B cells, which are a prerequisite for recovery from primary virus infections via skin or via blood.     

Treatment with the antigranulocyte monoclonal antibody RB6-8C5 impairs resistance of mice to gastrointestinal infection with Listeria monocytogenes

Treatment with the antigranulocyte monoclonal antibody (MAb) RB6-8C5 increased the severity of infection in mice intragastrically inoculated with Listeria monocytogenes. Most MAb RB6-8C5-treated mice died when inoculated intragastrically with as few as 4 x 10(4) L. monocytogenes bacteria, whereas most control mice survived intragastric inoculation with 4 x 10(8) L. monocytogenes bacteria. The increased severity of infection in MAb RB6-8C5-treated mice appeared to result from listerial multiplication in the spleen and liver rather than from local proliferation in the intestinal tract or mesenteric lymph nodes.     

The new parameters of motor unit potential in the diagnosis of neurogenic lesions in spike-triggered averaging electromyography

The chronic Pseudomonas aeruginosa lung infection in cystic fibrosis (CF) is characterized by a pronounced antibody response and microcolonies surrounded by numerous polymorphonuclear neutrophils (PMN). Poor prognosis is correlated with a high antibody response to P. aeruginosa antigens. An animal model of this infection was established in two strains of mice: C3H/HeN and BALB/c, generally known as Th1 and Th2 responders, respectively, which were challenged with alginate-embedded P. aeruginosa. Mortality was significantly lower in C3H/HeN compared to BALB/c mice (p < 0.025). P. aeruginosa was cleared more efficiently in C3H/HeN mice and significantly more C3H/HeN mice showed normal lung histopathology (p < 0.02), and we found significantly fewer microabscesses in C3H/HeN mice than in BALB/c mice (p < 0.005). In supernatants from P. aeruginosa antigen and concanavalin A-stimulated spleen cells from the two strains of mice, the interferon-(IFN-) gamma levels were higher, whereas IL-4 levels were lower in C3H/HeN mice than in BALB/c mice. The implications of these findings for CF patients with chronic P. aeruginosa lung infection are discussed.     

Erectile insufficiency as first symptom of HTLV I/II associated myelopathy. Case report

People infected with Trypanosoma cruzi remain so for life, yet only 30-40% of these individuals develop characteristic chagasic cardiomyopathies. Similarly, when infected with the Brazilian strain of T. cruzi, DBA/2 mice develop severe cardiac damage while B10.D2 mice do not. To better understand the immunological parameters that may be involved in the disease process, we have used this murine model (DBA/2 vs B10.D2) and compared the changes in cytokine production during the course of infection with T cruzi. Concanavalin A (Con A) stimulation of spleen cells harvested during the acute phase (day 30) resulted in similarly high levels of IFN-gamma in both mouse strains. However, the amount of IFN-gamma in supernatants from cultures of B10.D2 spleen cells initiated during the chronic phase (day 72) was at subacute levels, whereas secretion by chronic DBA/2 spleen cells remained high. In addition, Con A-stimulated spleen cells from acute DBA/2 mice produced approximately twice as much IL-10 and significantly more IL-4 than cells from B10.D2 mice. IL-4 secretion remained low by cells from chronic B10.D2 mice, but when using cells from chronic DBA/2 mice, levels continued to increase beyond the already high levels secreted by cells harvested during the acute phase. Proliferative responses to Con A stimulation by spleen cells from DBA/2 mice were significantly higher than those from B10.D2 mice in both the acute and chronic phases. These data suggest that enhanced responses in DBA/2 mice, which may be related to a higher parasite burden, a lack of down-regulation, and/or the onset of autoimmune phenomena, correlate with the more severe cardiomyopathy seen in pathopermissive mice.     

Leishmania major infection in C57BL/10 mice differing at the Lps locus: a new non-healing phenotype

The course of cutaneous leishmaniasis was examined in mice from two genetically closely related strains, C57BL/10ScCr (Cr) and C57BL/10ScSn (Sn). Sn mice are able to heal Leishmania major infections, while Cr mice are unable to heal. The cutaneous lesions of the Cr mice progressed continuously and the increase in lesion size was paralleled by an unrestricted growth of the parasites in vivo. Cr mice, in contrast to their Sn counterparts, are highly resistant to all effects of lipopolysaccharide (LPS). The nonhealing L. major infection in Cr mice is in sharp contrast to the course of infection in another endotoxin-nonresponder mouse strain, C3H/HeJ, which heal infections with L. major. Cr mice exhibit, in addition to the defective LPS responsiveness, an impaired interferon-gamma (IFN-gamma) response after infection with a variety of microorganisms. The insufficient activation of parasitized macrophages to kill intracellular L. major could be due to the inability of splenocytes from infected Cr mice to secrete IFN-gamma upon restimulation with L. major. IFN-gamma is essential for the efficient activation of parasitized macrophages to kill intracellular L. major by producing nitric oxide (NO). Although bone marrow-derived Cr macrophage do not produce NO in response to LPS, both Sn and Cr macrophages release NO upon stimulation with IFN-gamma and tumor necrosis factor, indicating that they are responsive to activation by these cytokines.     

The comparative histopathology of primary and secondary lesions in murine salmonellosis

In a primary infection, Swiss-Webster mice were injected i.p. with 10(2) or 10(3) virulent Salmonella typhimurium. Multiple microscopic acute abscesses with predominantly polymorphonuclear leucocytes (PMNs) were seen in the liver and the spleen beginning on the 4th day after infection. By the 7th day, these lesions had become enlarged and were gradually transformed into granulomas with central necrosis and peripheral mononuclear cells. The animals usually died within 12 days with massive systemic infection and degeneration of the tissues. In contrast, it was necessary to inoculate 10(6) virulent salmonella i.v. into mice immunized with avirulent S. thphimurium in order to initiate microscopically observable lesions in the liver and the spleen. These secondary lesions were characterized by the early appearance of minute granulomas composed almost entirely of histiocytic cells. They remained small and isolated, usually without central necrosis. Subsequent regression of the lesions and regeneration of normal tissue occurred after the 2nd week following infection. The animals usually survived such a challenge infection.     

Role of macrophages in acute murine cytomegalovirus infection

It has been recognized that macrophages play an important role in controlling virus infection in experimental animal models. To evaluate the role of macrophages in acute murine cytomegalovirus infection, macrophages in the spleen and the liver were eliminated by an intravenous injection of liposomes containing a cytolytic agent, dichloromethylene diphosphonate. The depletion of macrophages led to a significant increase of virus titer in the spleen and lungs in both susceptible BALB/c and resistant C57BL/6 mice during the first three days after intravenous infection. In the spleen, the increase of virus titer in macrophage-depleted BALB/c mice was much greater than that in NK cell-depleted mice. These results suggest that macrophages contribute to protection mainly by the mechanisms which are independent of NK cells during the first three days after infection. The increase of virus titer in macrophage-depleted C57BL/6 mice was as great as that in NK cell-depleted mice because of the high contribution of NK cells to protection in C57BL/6 mice. In the liver in both strains of mice, the effects of macrophage depletion on virus titer were not as much as those in the spleen and lungs. Furthermore, the local depletion of peritoneal macrophages resulted in a great increase of virus titer in the spleen at three days after intraperitoneal infection. We conclude that macrophages greatly contribute to decreasing the virus load in some organs possibly through either or both intrinsic and extrinsic mechanisms in the early phase of primary infection with murine cytomegalovirus.     

Age-related changes in the metabolism of acetylated low-density lipoproteins by peritoneal macrophages from C57BL/6CrScl mice

Macrophages are major precursors of foam cells in atherosclerotic lesions. Acetylated low-density lipoproteins (acetyl LDL) taken up by macrophages through scavenger receptors are degraded by lysosomes and the released cholesterol is re-esterified, leading to foam cell formation. The ability of resident peritoneal macrophages from C57BL/6CrScl mice to form foam cells in relation to the donor age was assessed by the cholesterol esterification and the metabolism of acetyl LDL. The incorporation of 14C-oleate (complexed to albumin) into cellular cholesteryl esters in the presence of acetyl LDL (100 micrograms/ml) was significantly greater in macrophages from senescent mice (24-25 months) than in cells from young (3-4 months) mice (p < .001). The degradation and cellular association of acetyl LDL by macrophages from senescent mice were significantly greater than macrophages from mature mice, (p < .001 and p < .01, respectively), whereas the binding of acetyl LDL was similar in peritoneal macrophages from mature and senescent mice. These results suggest that the uptake and degradation of acetyl LDL, and the re-esterification by macrophages increase with advancing age and that the ability of macrophages to form foam cells increases with aging. The enhanced ability of senescent macrophages to form foam cells might contribute to the development and progression of atherosclerosis related to the aging process.     

Protective role of nitric oxide in ocular toxoplasmosis

AIMS: To evaluate the role of nitric oxide (NO) in ocular involvement during systemic toxoplasmosis. METHODS: C57B1/6 mice were infected with Toxoplasma gondii strain ME49. The synthesis of NO was inhibited by an intraperitoneal injection of aminoguanidine every 8 hours, starting on the day of infection. Control infected mice received phosphate buffered saline vehicle alone. After 14 days, the ocular lesions were evaluated by histopathological examination. The expression of NO synthase induced in the spleen by toxoplasma infection was evaluated by immunostaining. The production of NO by the spleen cells of infected mice was measured by the colorimetric assay of Griess in the supernatant of cultures stimulated with toxoplasma antigen or concanavalin A. RESULTS: The inhibition of NO production in T gondii infected mice resulted in a marked increase in the symptoms of ocular inflammation. We observed a strong induction of NO synthase expression in the spleen of infected animals. In culture, the spleen cells from these mice produced high levels of NO in response to T gondii antigens. This elevation of NO synthesis was suppressed in the presence of aminoguanidine. CONCLUSION: This study indicates that NO plays a crucial role in the protection against T gondii infection as reflected by the severity of the ocular involvement.     

Influence of vitamin D3 infusion and dietary calcium on secretion of interleukin 1, interleukin 6, and tumor necrosis factor in mice infected with Mycobacterium paratuberculosis

OBJECTIVE: To study the effects of 1,25(OH)2D3 and calcium (Ca) on splenocyte cytokine secretion during Mycobacterium paratuberculosis infection. DESIGN: Mice were assigned to the following treatments: 1-noninfected, 2-infected, 3-noninfected/1,25(OH)2D3, 4-infected/1,25(OH)2D3, and 5-infected/low-Ca diet (0.15%). ANIMALS--Male beige mice averaging 6 weeks of age and 20 g in body weight. PROCEDURE: After acclimation to their diets, mice in treatments 2, 4, and 5 were inoculated IV with 10(8) colony-forming units of M paratuberculosis. At 1, 6, and 12 months after infection, mice in treatment groups 3 and 4 had miniosmotic pumps implanted subcutaneously that delivered 13 ng of 1,25(OH)2D3/day for 14 days. Treatment 5 was included as a control for comparison with treatment 4 because low dietary Ca should increase endogenous 1,25(OH)2D3 values. Splenocytes were isolated from mice at 1, 6, and 12 months and stimulated in vitro with medium alone (nonstimulated), lipopolysaccharide (LPS), concanavalin A, and M paratuberculosis whole-cell sonicate (MpS). RESULTS: Production of interleukin 6 after stimulation with LPS, concanavalin A, or MpS was higher (P < 0.05) for splenocytes isolated from mice fed the low-Ca diet, compared with control infected mice 1 and 6 months after infection. Interleukin 1 and tumor necrosis factor activities were increased (P < 0.05) in splenocytes cultured with LPS and MpS after isolation from mice of the low-Ca group. Mice infused with 1,25(OH)2D3 had higher (P < 0.05) interleukin 1 secretion after stimulation of splenocytes with LPS and higher (P < 0.05) tumor necrosis factor production after incubation with MpS. CONCLUSION: 1,25(OH)2D3 and low dietary Ca increase cytokine secretion in mice infected with M paratuberculosis.     

Expression of leptin receptor isoforms in rat brain microvessels

Current evidence suggests that host defense in respiratory mycoplasmosis is dependent on both innate and humoral immunity. To further delineate the roles of innate and adaptive immunity in antimycoplasmal defenses, we intranasally infected C3H/HeSnJ-scid/scid (C3H-SCID), C3H/HeSnJ (C3H), C57BL/6J-scid/scid (C57-SCID), and C57BL/6N (C57BL) mice with Mycoplasma pulmonis and at 14 and 21 days postinfection performed quantitative cultures of lungs and spleens, quantification of lung lesions, and histopathologic assessments of all other major organs. We found that numbers of mycoplasmas in lungs were associated with genetic background (C3H susceptible, C57BL resistant) rather than functional state of adaptive immunity, indicating that innate immunity is the main contributor to antimycoplasmal defense of the lungs. Extrapulmonary dissemination of mycoplasmas with colonization of spleens and histologic lesions in multiple organs was a common occurrence in all mice. The absence of adaptive immune responses in severe combined immunodeficient (SCID) mice resulted in increased mycoplasmal colonization of spleens and lesions in extrapulmonary sites, particularly spleens, hearts, and joints, and also reduced lung lesion severity. The transfer of anti-M. pulmonis serum to infected C3H-SCID mice prevented extrapulmonary infection and disease, while the severity of lung lesions was restored by transfer of naive spleen cells to infected C3H-SCID mice. Collectively, our results strongly support the conclusions that innate immunity provides antimycoplasmal defense of the lungs and humoral immunity has the major role in defense against systemic dissemination of mycoplasmal infection, but cellular immune responses may be important in exacerbation of mycoplasmal lung disease.     

Cytolytic activity of pulmonary and systemic lymphoid cells from C57BL/6 mice following intrapulmonary or intraperitoneal immunization with allogeneic tumor cells

In order to demonstrate whether specific cytotoxic T cells could be induced in lung parenchyma, C57BL/6 mice were immunized by the intrapulmonary route with allogenetic tumor cells (P815). Ten days after administration of 20 x 10(6) allogeneic cells, peak concentrations of cytotoxic cells were found in lung, tracheobronchial lymph node, and spleen. With reduction in immunizing dose, lytic activity disappeared from spleen and lymph node, but persisted in lung. The cytolytic activity was specific for the immunizing alloantigen, was abolished by antitheta serum, and could not be attributed to macrophages. For comparison, C57BL/6 mice were immunized by the intraperitoneal route with 20 x 10(6) P815 cells. The expected cytolytic activity was found in spleen and lymph nodes: however, unexpectedly high levels of cytolytic activity were also found in pulmonary lymphocytes. This activity was confirmed using a wide range of effector to largest cell ratios in the assay system. Quantitative cytolytic assays demonstrated that the maximum rate of cytolysis by pulmonary lymphocytes obtained from mice immunized intraperitoneally exceeded by 10- to 20-fold the rate of cytolysis by pulmonary lymphocytes obtained from mice receiving intrapulmonary immunization. These data demonstrate that cytolytic T-lymphocytes appear in lung parenchyma after either intrapulmonary or intraperitoneal immunization and that the intraperitoneal route is far more efficient than the intrapulmonary route. This cell-mediated immune mechanism potentially is available for host defense of respiratory tissue.