RNA-binding protein conserved in both microtubule- and microfilament-based RNA localization

IL-12 is a key cytokine in the development of Th1 responses. IL-12 production by antigen-presenting cells (APC) can be induced by the interaction between CD40 on the APC and CD40 ligand (CD40L) expressed on T cells after activation. Our previous study indicated that in dendritic cells (DC), the only APC that can activate naive T(h) cells efficiently, the mere CD40 engagement is insufficient to induce IL-12 production. The aim of the present study was to dissect the conditions for efficient IL-12 production by DC further. Using populations of naive and memory Th cells, recombinant CD40L, neutralizing and blocking antibodies, and by determining IFN-gamma production and CD40L expression levels, we here show that T cell-induced IL-12 production by DC results from the action of two signals, mediated by CD40L and IFN-gamma, and that the inability of naive T(h) cells to induce IL-12 production resides in their inability to produce IFN-(gamma). Other factors than CD40L and IFN-gamma can provide the required signals for IL-12 production by DC, as either factor could be replaced by lipopolysaccharide (LPS). The two-signal requirement proved unique for the production of IL-12, since either CD40 engagement or LPS was sufficient for the efficient production of tumor necrosis factor-alpha, IL-8 and the p40 subunit of IL-12, and may be considered as a safety mechanism for optimal control of potentially harmful T(h)1 responses.     

Dendritic cells derived in vitro from acute myelogenous leukemia cells stimulate autologous, antileukemic T-cell responses

We have previously reported that leukemic dendritic cells (DC) can be generated ex vivo from myelomonocytic precursors in chronic myelogenous leukemia. In this study we report the generation of DC from acute myelogenous leukemia (AML) cells and their potent ability to stimulate leukemia-specific cytolytic activity in autologous lymphocytes. DC were generated in vitro using granulocyte-macrophage colony-stimulating factor +interleukin-4 in combination with either tumor necrosis factor-alpha or CD40 ligand (CD40L). Cells from 19 AML patients with a variety of chromosomal abnormalities were studied for their ability to generate DC. In all but 1 case, cells with the morphology, phenotypic characteristics, and T-cell stimulatory properties of DC could be generated. These cells expressed high levels of major histocompatibility complex class I and class II antigens as well as the costimulatory molecules B7-2 and ICAM-1. In three cases these cells were determined to be of leukemic origin by fluorescence in situ hybridization for chromosomal abnormalities or Western blotting for the inv(16) fusion gene product. Autologous lymphocytes cocultured with AML-derived DC (DC-AL) were able to lyse autologous leukemia targets, whereas little cytotoxicity was noted against autologous, normal cells obtained from the patients during remission. We conclude that leukemia derived DC may be useful for immunotherapy of many AML patients.     

Ligation of CD40 on dendritic cells triggers production of high levels of interleukin-12 and enhances T cell stimulatory capacity: T-T help via APC activation

We investigated the possibility that T helper cells might enhance the stimulatory function of dendritic cells (DCs). We found that ligation of CD40 by CD40L triggers the production of extremely high levels of bioactive IL-12. Other stimuli such as microbial agents, TNF-alpha or LPS are much less effective or not at all. In addition, CD40L is the most potent stimulus in upregulating the expression of ICAM-1, CD80, and CD86 molecules on DCs. These effects of CD40 ligation result in an increased capacity of DCs to trigger proliferative responses and IFN-gamma production by T cells. These findings reveal a new role for CD40-CD40L interaction in regulating DC function and are relevant to design therapeutic strategies using cultured DCs.     

Sensitized lymphocytes and CD40 ligation augment interleukin-12 production by human dendritic cells in response to Toxoplasma gondii

Dendritic cells (DC) are potent antigen-presenting cells that can stimulate T cell responses by secreting cytokines. During Toxoplasma gondii infection, host immunity is mediated by interferon-gamma, which is induced by interleukin-12 (IL-12). Whether T. gondii infection would stimulate human DC to produce IL-12 was determined. DC were generated from human peripheral blood mononuclear cells cultured with recombinant human granulocyte-macrophage colony-stimulating factor and recombinant human IL-4. DC secreted high levels of IL-12 in response to lipopolysaccharide but not to either live T. gondii tachyzoites or soluble antigen. However, IL-12 production in response to T. gondii was observed when DC were cocultured in contact with lymphocytes isolated from seropositive donors. Ligation of CD40:CD154 was partially essential for IL-12 secretion. These data demonstrate that signals obtained from contact with sensitized lymphocytes are critical for human DC to secrete IL-12 in response to T. gondii.     

Cross-linking of the CD40 ligand on human CD4+ T lymphocytes generates a costimulatory signal that up-regulates IL-4 synthesis

Although there is good evidence that the induction of IL-4 synthesis in CD4+ T lymphocytes is favored by Ag presentation by B cells and not macrophages, the precise molecular signals provided by B cells to T cells that enhance IL-4 synthesis are not clear. To examine this issue, we established an APC-independent system to activate highly purified T cells and induce cytokine synthesis, using immobilized mAbs against several T cell surface molecules, including CD3, CD28, and the CD40 ligand (CD40L). The counter-receptors for all three of these molecules are expressed on B cells, and include CD40, which is expressed primarily on B cells, but also on dendritic cells and thymic epithelium. We found that IL-4 synthesis was greatly enhanced by triggering of CD40L on the T cell surface in conjunction with ligation of CD3/TCR and CD28, whereas ligation of CD3/TCR and CD28 in the absence of CD40L triggering resulted in little or no IL-4 synthesis. CD40L costimulation greatly enhanced IL-4 synthesis both in T cells from normal nonallergic adult subjects as well as in naive T cells from cord blood. Furthermore, we demonstrated that IL-4 synthesis was optimally enhanced when the strength of the CD3/TCR signal was limiting, while IL-4 synthesis was inhibited when CD3/TCR stimulation was maximal. These studies confirm that IL-4 synthesis can be induced in normal T lymphocytes in the absence of exogenous IL-4, and demonstrate that CD40L costimulation is of fundamental importance in regulation of IL-4 production. In addition, these findings provide a mechanism by which B cells preferentially enhance IL-4 synthesis in T cells at low Ag concentrations.     

In vitro expansion and characterization of dendritic cells derived from human bone marrow CD34+ cells

Dendritic cells (DC), as professional antigen-presenting cells, play a major role in stimulating naive T cell responses in vivo and in vitro, and may exacerbate or modulate T lymphocyte-mediated reactions, such as interactions between a hematopoietic graft and the recipient, eg GVHD and graft-versus-leukemia. Here, we describe a two-stage cell culture system for expansion of functionally active human DC from CD34+ marrow precursors. Optimal outgrowth was achieved by initially culturing CD34+ cells for 5 days in medium containing GM-CSF, MGF and TNF-alpha. Substitution of CD40L and IL-4 for TNF-alpha during a subsequent 5-day subculture increased DC content, such that by 10 days the cultures contained approximately 40% DC as determined by immunophenotype and morphology. An increase in DC purity to 84% at 10 days was achieved by immunomagnetic separation for CD1a+ cells from 5-day cultures and subculturing these cells in medium with IL-4 and CD40L. Reversing the sequence of growth factors during culture and subculture decreased the yield and purity of DC. Expression of CD80 and CD86 was enhanced by adding CD40L and IL-4, and the DC showed stimulatory activity in MLC. In conclusion, we have described a simple two-stage culture system to generate functional DC from CD34+ marrow precursors.     

健康人外周血树突状细胞的体外诱导及其功能分析

目的 分析以健康人AB血清与rhCD40L体外诱导健康人外周血树突状细胞(DC)的功能.方法 对健康人外周血单个核细胞进行体外培养,在以健康人AB血清为基础的培养体系中加入粒细胞巨噬细胞集落刺激因子(GM-CSF)、重组人白细胞介素(rhIL)-4、rhCD40L等细胞因子,诱导单个核细胞分化形成DC,采用倒置显微镜及瑞特-吉姆萨染色观察,流式细胞术行DC表型鉴定,四甲基偶氮唑蓝比色(MTT)法进行混合淋巴细胞反应(MLR),检测其抗原刺激能力,酶联免疫吸附(ELISA)法检测DC培养上清IL-12的分泌.结果 培养7 d后的细胞具有典型的DC形态,并上调表达DC特征性表面分子CD83及共刺激分子CD40、CD80、CD86,第0、1、3、5、7天,5个时间点间CD83、CD40、CD80、CD86、CD14表达差异有统计学意义(F值分别为50.253、243.769、248.181、191.267、226.339,均P＜0.05).培养后的DC可较强地刺激同种自体淋巴细胞增殖,GM-CSF加rhIL-4、rhCD40L组较GM-CSF加rhIL-4组刺激反应能力强.培养的DC自培养第5天始即有IL-12分泌,未加CD40L组IL-12 p40分泌量为(42.92±1.54)pg/ml,加CD40L组为(136.18±5.27)pg/ml;培养第7天,IL-12 p40分泌明显增多,两组分别为(60.09±2.27)pg/ml及(322.30±30.60)pg/ml,差异有统计学意义(t=-44.941、-22.611,均P＜0.05).结论 健康人外周血单个核细胞可在以健康人AB血清与rhCD40L为主的培养体系中诱导成DC.     

Th1 cells induce and Th2 inhibit antigen-dependent IL-12 secretion by dendritic cells

Dendritic cells are the most relevant antigen-presenting cells (APC) for presentation of antigens administered in adjuvant to CD4+ T cells. Upon interaction with antigen-specific T cells, dendritic cells (DC) expressing appropriate peptide-MHC class II complexes secrete IL-12, a cytokine that drives Th1 cell development. To analyze the T cell-mediated regulation of IL-12 secretion by DC, we have examined their capacity to secrete IL-12 in response to stimulation by antigen-specific Th1 and Th2 DO11.10 TCR-transgenic cells. These cells do not differ either in TCR clonotype or CD40 ligand (CD40L) expression. Interaction with antigen-specific Th1, but not Th2 cells, induces IL-12 p40 and p75 secretion by DC. The induction of IL-12 production by Th1 cells does not depend on their IFN-gamma secretion, but requires direct cell-cell contact mediated by peptide/MHC class II-TCR and CD40-CD40L interactions. Th2 cells not only fail to induce IL-12 secretion, but they inhibit its induction by Th1 cells. Unlike stimulation by Th1, inhibition of IL-12 production by Th2 cells is mediated by soluble molecules, as demonstrated by transwell cultures. Among Th2-derived cytokines, IL-10, but not IL-4 inhibit Th1-driven IL-12 secretion. IL-10 produced by Th2 cells appears to be solely responsible for the inhibition of Th1 -induced IL-12 secretion, but it does not account for the failure of Th2 cells to induce IL-12 production by DC. Collectively, these results demonstrate that Th1 cells up-regulate IL-12 production by DC via IFN-gamma-independent cognate interaction, whereas this is inhibited by Th2-derived IL-10. The inhibition of Th1 -induced IL-12 production by Th2 cells with the same antigen specificity represents a novel mechanism driving the polarization of CD4+ T cell responses.     

Intraepithelial lymphocytes and their recognition of non-classical MHC molecules

Recent studies of the TCR alpha and beta chains expressed by normal human IELs suggest that these intestinal lymphocytes are directed at a limited set of antigens, presumably on intestinal epithelial cells in view of their anatomic location. The direct sequence analysis of these cells has indicated that they are oligoclonal and cannot, therefore, be responding to the complex mixture of antigens which are present in the lumen. The abundant expression of the CD8 accessory molecule by the IELs, in addition, indicates that these putative intestinal epithelial cell antigens are presented by MHC class I or I-like molecules. The expression of CD8 also suggests that these cells function biologically in part as cytolytic T lymphocytes which is consistent with a variety of functional studies. Taken together with their expression of the CD45RO isoform, these phenotypic and functional observations suggest that iIELs are cytolytic, memory cells which are responsive to an extremely limited number of antigens bound to major histocompatibility complex (MHC) class I or class I-like molecules. Several non-polymorphic MHC class I-like molecules such as Qa, the thymus leukemia antigen (TL) and CD1 in the mouse and CD1 in human represent important candidate ligands for these oligoclonal iIELs. TL and CD1 are expressed specifically by murine intestinal epithelial cells. In humans, CD1d is constitutively expressed by intestinal epithelial cells. In addition, we have isolated iIEL T cell clones which specifically recognize members of the CD1 gene family when expressed on a transfected B cell line that lacks HLA-A and B and have shown that the proliferation of peripheral blood T cells to intestinal epithelial cells is CD1d dependent. Thus, the evidence to date strongly implicate the nonpolymorphic, class Ib molecules as novel restriction elements for unique populations of lymphocytes within the intestinal epithelium.     

Total hip arthroplasty: imaging evaluation

Crosslinking of CD28 receptors on resting T lymphocytes by B7 costimulatory molecules expressed by antigen-presenting cells (APCs) plays a critical role in T-cell activation. Human melanomas express major histocompatibility complex (MHC)-restricted tumor-associated antigens that can be recognized by cytotoxic T lymphocytes (CTL), yet they remain poorly immunogenic. One mechanism for the failure of T-cell response is the lack of expression of costimulatory molecules by human melanoma cells. We have transfected the B7-1 gene into three HLA-A2-expressing human melanoma cell lines, and studied their capacity to stimulate primary human T cells. B7-expressing melanoma cells were excellent inducers of T-cell proliferation, cytokine production, and cytolytic activity in allogeneic mixed lymphocyte cultures through a process dependent on the function of the T-cell receptor as well as interactions between B7:CD28, CD2:LFA-3, and LFA-1:ICAM-1. Subset analysis demonstrated that CD4+ T cells or addition of exogenous interleukin-2 was required for the induction of CD8+ CTL. Untransfected parental melanoma cells were inert as APCs in these cultures. Rotating stimulation of T cells with the three B7-expressing cell lines led to the generation of T-cell lines that were cytolytic for HLA-A2+ melanoma cells and other HLA-A2+ targets that were pulsed with HLA-A2-restricted MART-1 peptides. These data demonstrate that expression of B7-1 by human melanoma cells converts them into effective APCs for the in vitro induction of MHC-restricted, melanoma-specific CTL.     

Blockade of the CD40-CD40 ligand pathway potentiates the capacity of donor-derived dendritic cell progenitors to induce long-term cardiac allograft survival

BACKGROUND: Failure of costimulatory molecule-deficient donor dendritic cells (DCs) to induce indefinite allograft acceptance may be a result of the 'late" up-regulation of these molecules on the DCs after interaction with host T cells. Ligation of CD40 on antigen-presenting cells by its cognate ligand CD40L is thought to induce expression of CD80 (B7-1) and CD86 (B7-2). We examined the influence of anti-CD40L monoclonal antibody (mAb) on the capacity of donor-derived DC progenitors to induce long-term allograft survival. METHODS: High purity DC progenitors were grown from B10 (H2b) mouse bone marrow in granulocyte-macrophage colony-stimulating factor and transforming growth factor beta1 (TGFbeta1). Mature DC were propagated in granulocyte-macrophage colony-stimulating factor and interleukin-4. Their phenotype was characterized by flow cytometric analysis and their function by mixed leukocyte reactivity. Anti-donor cytotoxic T lymphocyte activity in grafts and spleens of vascularized heart allograft recipients was also assessed. RESULTS: The TGFbeta3-cultured cells were (1) DEC 205-positive, MHC class II-positive, CD80dim, CD86dim, and CD40dim, (2) poor stimulators of naive allogeneic T-cell proliferation, and (3) able to prolong significantly B10 cardiac allograft survival in C3H (H2k) recipients when given (2 x 10[6] i.v.) 7 days before organ transplantation (median survival time [MST] 26 days vs. 12 days in controls, and 5 days in interleukin-4 DC-treated animals). Their allostimulatory activity was further diminished by addition of anti-CD40L mAb at the start of the mixed leukocyte cultures. Anti-CD40L mAb alone (250 microg/mouse, i.p.; day -7) did not prolong cardiac graft survival (MST 12 days). In contrast, TGFbeta-cultured DCs + anti-CD40L mAb extended graft survival to a MST of 77 days, and inhibited substantially the anti-donor cytotoxic T lymphocyte activity of graft-infiltrating cells and host spleen cells assessed 8 days after transplant. CONCLUSIONS: The CD40-CD40L pathway appears important in regulation of allogeneic DC-T-cell functional interaction in vivo; its blockade increases markedly the potential of costimulatory molecule-deficient DCs of donor origin to induce long-lasting allograft survival.     

Fas expression and apoptosis in human B cells

Mechanisms of B cell apoptosis are critical in reducing aberrant B cell proliferations such as those that arise in autoimmune disease and in B cell malignancies. The physiologic interaction of CD4+ helper T cells and B lymphocytes has been extensively studied over the past two decades. Although CD4+ T cells are considered primarily to offer positive costimulatory signals for B cell differentiation into active immunoglobulin-secreting cells, recent studies have shown that CD4+ T cells are crucial in downregulating the humoral immune response. In the course of cognate interaction between CD40 ligand (CD40L)-bearing CD4+ T cells and CD40-expressing germinal center B cells, CD40 ligation results in augmented Fas expression at the B cell surface. Like CD40L, Fas ligand is expressed on activated CD4+ Th1 cells and when bound to Fas receptor on the B cell surface, initiates an apoptotic signal in that cell. Thus, CD4+ T cells limit the growth of autologous germinal center B cells by first inducing Fas expression and then instigating a death signal via Fas ligand. In this work, we will consider these observations about CD4+ T-cell-induced, Fas-mediated B cell death in the context of other factors that affect apoptosis in B cells, normal and malignant.     

ATP-induced, P2U purinoceptor-mediated constriction of isolated, perfused mesenteric beds of the rat

Upon antigen encounter epidermal Langerhans cells (LC) and dendritic cells (DC) emigrate from peripheral organs and invade lymph nodes through the afferent lymphatic vessels and then assemble in the paracortical T cell zone and present antigen to T lymphocytes. Part of this process is mimicked by metastasizing tumor cells. Since splice variants of CD44 promote metastasis to lymph nodes we explored the expression of CD44 proteins on migrating LC and DC. We show that following antigen contact, LC and DC upregulate pan CD44 epitopes and epitopes encoded by variant exons v4, v5, v6 and v9. Antibodies against CD44 epitopes arrest LC in the epidermis, prevent the binding of activated LC and DC to the T cell zones of lymph nodes, and severely inhibit their capacity to induce a delayed type hypersensitivity reaction to a skin hapten in vivo. Our results demonstrate that CD44 splice variant expression is obligatory for the migration and function of LC and DC.     

Cloning of BY55, a novel Ig superfamily member expressed on NK cells, CTL, and intestinal intraepithelial lymphocytes

Expression of the BY55 protein has been shown to be tightly associated with NK and CD8+ T lymphocytes with cytolytic effector activity. To determine the function of this protein, we molecularly cloned BY55 cDNA. The cDNA sequence predicts a cysteine-rich, glycosylphosphatidylinositol-anchored protein of 181 amino acids with a single Ig-like domain weakly homologous to killer inhibitory receptors. Reduction and carboxyamidomethylation of immunoprecipitated BY55 gave a band of 27 kDa, whereas reduction alone led to an 80-kDa species, suggesting that BY55 is a tightly disulfide-linked multimer. RNA blot analysis revealed BY55 mRNAs of 1.5 and 1.6 kb whose expression was highly restricted to NK and T cells. BY55 was expressed on the CD56dim, CD16+ subset of NK cells, which have high cytolytic activity, but was not expressed and was not induced on the CD56bright, CD16-subset of NK cells, a subset with high proliferative, but low cytolytic, capacity. In human tissues, BY55 mRNA was expressed only in spleen, PBL, and small intestine (in gut lymphocytes). BY55 was expressed on all intestinal intraepithelial lymphocytes, which were predominantly CD3+TCRalpha/beta+CD4-CD8+CD11b+CD28-CD45RO+C D56-CD101+CD103+ (alphaEbeta7 integrin). In addition, BY55 was expressed on most CD8+CD28- peripheral blood T cells. These phenotypic relationships suggest that CD8+CD28+ precursor CTL may terminally differentiate into CD8+CD28-BY55+ effector CTL and that some of the peripheral blood CD8+CD28- subset may represent recirculation from mucosal epithelial immune sites.     

Uptake of Leishmania major amastigotes results in activation and interleukin 12 release from murine skin-derived dendritic cells: implications for the initiation of anti-Leishmania immunity

Epidermal Langerhans cells (LC) are immature dendritic cells (DC) located in close proximity to the site of inoculation of infectious Leishmania major metacyclic promastigotes by sand flies. Using LC-like DC expanded from C57BL/6 fetal skin, we characterized interactions involving several developmental stages of Leishmania and DC. We confirmed that L. major amastigotes, but not promastigotes, efficiently entered LC-like DC. Parasite internalization was associated with activation manifested by upregulation of major histocompatibility complex (MHC) class I and II surface antigens, increased expression of costimulatory molecules (CD40, CD54, CD80, and CD86), and interleukin (IL)-12 p40 release within 18 h. L. major-induced IL-12 p70 release by DC required interferon gamma and prolonged (72 h) incubation. In contrast, infection of inflammatory macrophages (Mphi) with amastigotes or promastigotes did not lead to significant changes in surface antigen expression or cytokine production. These results suggest that skin Mphi and DC are infected sequentially in cutaneous leishmaniasis and that they play distinct roles in the inflammatory and immune response initiated by L. major. Mphi capture organisms near the site of inoculation early in the course of infection after establishment of cellular immunity, and kill amastigotes but probably do not actively participate in T cell priming. In contrast, skin DC are induced to express increased amounts of MHC antigens and costimulatory molecules and to release cytokines (including IL-12 p70) by exposure to L. major amastigotes that ultimately accumulate in lesional tissue, and thus very likely initiate protective T helper cell type 1 immunity.     

IL-10 impacts autoimmune diabetes via a CD8+ T cell pathway circumventing the requirement for CD4+ T and B lymphocytes

IL-10 is essential for an early phase of diabetes in nonobese diabetic (NOD) mice, but later becomes protective against its development. The mechanism by which IL-10 mediates the pathway to diabetes in these mice is unknown. Herein, we dissected the cellular and costimulation requirements for diabetes in transgenic (tg) NOD mice that expressed IL-10 in their pancreatic islets (IL-10-NOD mice). We found that IL-10 alone did not cause diabetes because the offspring (IL-10-NOD-scid mice) from back-crosses of IL-10-NOD mice with NOD-scid mice had no diabetes. Moreover, these IL-10-NOD-scid mice were free of lymphocytic infiltration. Treatment of IL-10-NOD mice with depleting anti-CD4 mAb or control mAb had no effect on diabetes. Surprisingly, depletion of CD8+ T cells by treatment with the corresponding mAb inhibited diabetes without attenuating insulitis, demonstrating a critical role for CD8+ T cells in the disease process. Interestingly, B cell-deficient IL-10-NOD mice readily developed diabetes with kinetics and incidence similar to those observed in wild-type mice, demonstrating that B lymphocytes as APCs were not required in the disease process. Administration of anti-CD40 ligand (CD40L) mAb did not prevent disease, indicating that CD40/CD40L costimulation is not required for diabetes in IL-10-NOD mice. Immunization of IL-10-NOD mice with CFA or heat-shock protein 65, known to block diabetes in NOD mice, had no effect on their diabetes. We demonstrate that IL-10 contributes early to the pathology of diabetes via a CD8+ T cell pathway, eliminating the requirement for B lymphocytes and CD40-CD40L costimulation. Our findings provide a mechanism for the participation of IL-10 in the early development of diabetes.     

The expression of CD26 and CD40 ligand is mutually exclusive in human T-cell non-Hodgkin's lymphomas/leukemias

CD26 and CD40 ligand (CD40L) are surface molecules on human activated T lymphocytes that play a critical role in the regulation of lymphopoiesis. Both molecules are expressed on a restricted fraction of human T-cell non-Hodgkin's lymphomas (NHL)/leukemias; however, little is known about their functional and/or clinical significance in these disorders. In this study, the pattern of expression of CD40L was compared with that of the CD26 molecule. A series of 67 human T-cell NHL/leukemias and a panel of leukemia/lymphoma T-cell lines were evaluated by immunohistochemistry, flow cytometry, and RNA studies. The overall frequency of CD26+ and CD40L+ samples was rather similar (25/67 [37%] v 18/67 [27%]). However, the majority of CD26-expressing cases clustered in the lymphoblastic lymphomas (LBL)/T-acute lymphoblastic leukemias (ALL; 12/23) and CD30+ anaplastic large-cell (ALC) lymphomas (5/8), whereas CD40L+ lymphomas included a large fraction of mycosis fungoides (11/21 [52%]). CD26 and CD40L coexpression was found only in 2 myocosis fungoides cases and 1 small lymphocytic lymphoma. Thus, the expression of the two antigens was mutually exclusive in almost all T-cell lymphomas/leukemias. Accordingly, lymphoma cell lines expressed either one of the molecules or the relative amounts of CD26 and CD40L were inversely proportional. In contrast, reactive T lymphocytes from patients with non-neoplastic T-cell expansions and in vitro activated CD3+ or CD4+ normal T cells were found to coexpress CD40L and CD26. Results of a multivariate analysis showed that the expression of CD26 in T-cell LBL/ALL patients was associated to a worse outcome in terms of survival, as compared with patients with CD26- tumors (P < or = .0001). Based on our results, it can be concluded that, (1) as opposed to activated or reactive normal T cells, the expression of CD26 and of CD40L is mutually exclusive in human T-cell lymphomas/leukemias; (2) expression of CD26 is restricted to aggressive pathologic entities, such as T-cell LBL/ALL and T-cell CD30+ ALC lymphomas, whereas CD40L is expressed on slow progressing diseases such as mycosis fungoides; and (3) within the T-cell LBL/ALL group of tumors, CD26 may identify a subset of poor prognosis patients.     

T cells from patients with Hodgkin's disease have a defective T-cell receptor zeta chain expression that is reversible by T-cell stimulation with CD3 and CD28

To investigate the mechanisms underlying the deficiency of T lymphocytes from patients with Hodgkin's disease, we investigated the expression of the T-cell receptor (TCR) zeta chain in patients with Hodgkin's disease. By flow cytometry using an anti-zeta chain monoclonal antibody, peripheral blood T lymphocytes from patients with untreated Hodgkin's disease were shown to express decreased levels of the TCR zeta chain. After stimulation by combined CD3 and CD28 cross-linking, T cells from Hodgkin's disease patients upregulated zeta chain protein expression to normal values within 48 hours and achieved a cytolytic potential and levels of interleukin (IL)-2 secretion that were not different from T cells obtained from healthy controls. These results show that downregulation of the TCR zeta chain in Hodgkin's T lymphocytes is a reversible event. Costimulation of CD3 and CD28 is a novel approach for overcoming the T-cell deficiency in Hodgkin's disease and might be exploited clinically. As upregulation of the zeta chain can also be achieved using bispecific monoclonal antibodies (BI-MoAbs) with specificity for tumor antigens and CD3 and CD28, respectively, an immunotherapy with CD3/CD30 and CD28/CD30 Bi-MoAbs may overcome and should therefore, not be jeopardized by the inherent T-cell deficiency in patients with Hodgkin's disease.     

T-lymphocyte downregulation after acute viral infection is not dependent on CD95 (Fas) receptor-ligand interactions

Infection of mice with lymphocytic choriomeningitis virus (LCMV) causes a major expansion of CD8+ T cells followed by a period of immune downregulation that coincides with the induction of lymphocyte apoptosis in the mouse spleen. CD95 (Fas) and its ligand are important for regulating peripheral T-lymphocyte numbers and can mediate apoptosis of mature T lymphocytes. We infected CD95- and CD95L-deficient mice (lpr and gld, respectively) with LCMV to determine if the immune downregulation that occurred following resolution of the LCMV infection was due to a CD95-dependent apoptotic mechanism. Lymphocytes from LCMV-infected lpr and gld mice were capable of normal T-cell expansion and cytolytic function but were, in contrast to activated cells from normal virus-infected mice, relatively more resistant to T-cell receptor-induced apoptosis in vitro. However, in vivo there were significant numbers of apoptotic cells in the spleens of lpr and gld mice recovering from the infection, and the T-cell number and cytolytic activity decreased to normal postinfection levels. Thus, CD95 is not required for the immune downregulation of the CD8+-T-lymphocyte response following acute LCMV infection.