Allorecognition of isolated, denatured chains of class I and class II major histocompatibility complex molecules. Evidence for an important role for indirect allorecognition in transplantation.

Classical RT1-A class I and RT1-B class II major histocompatibility complex (MHC) molecules were purified from DA (RT1avl) spleens, and the individual chains separated and purified by preparative polyacrylamide gel electrophoresis in sodium dodecyl sulfate. LEW (RT1l) rats were immunized with the pure class I heavy chain, the RT1-B alpha chain and the RT1-B beta chain with the aim of priming to indirect allorecognition (i.e. after processing and presentation of DA MHC chains on LEW antigen-presenting cells) in the absence of any priming to direct allorecognition (i.e. to whole, undenatured, dimeric DA MHC molecules). LEW rats immunized with each of the three DA MHC chains produced alloantibodies to these chains, suggesting that indirect allorecognition did occur, because of the requirement for cognate recognition of B cells by T helper cells. This also demonstrated polymorphism of all three chains between the DA and LEW strains. The antibodies to the isolated, denatured MHC chains did not react to the whole MHC molecules on DA cells, with the possible exception of very weak reactions in some class I heavy chain-immunized rats. DA skin grafts placed on LEW recipients immunized with each of the DA MHC chains were rejected in an accelerated fashion. Following DA skin grafting, there was an accelerated production of antibodies to whole, undenatured class I MHC molecules, even in the LEW rats preimmunized with RT1-B alpha and RT1-B beta chains. These data suggest that indirect allorecognition can play an important role in the effector mechanisms of allograft rejection, and demonstrate T helper priming as one possible mechanism whereby this might be effective.     

CD8+ cells suppress oil-induced arthritis

Oil-induced arthritis is a genetically restricted polyarthritis that develops in the DA rat after injection of the mineral oil Freund's incomplete adjuvant. Here, we investigated the role of the potentially disease-limiting cell populations CD8+ T cells, gammadelta T cells, natural killer (NK) cells and NK T cells in inguinal lymph nodes for the development of this adjuvant-induced arthritis. Flow cytometry analysis before and at disease onset revealed a higher proportion of lymph node T cells expressing NKR-P1 in the disease-resistant LEW.1AV1 compared with the disease-susceptible DA strain, suggesting that NK T cells might be disease protective. However, prophylactic in vivo administration of an anti-NKR-P1 MoAb (clone 10/78) did not consistently affect the disease course. The proportion of CD8+ T cells and the ratio CD4+/CD8+ T cells in inguinal lymph nodes did not differ significantly between DA and LEW.1AV1 rats before or at disease onset. Nevertheless, prophylactic in vivo depletion of CD8+ cells by the OX8 MoAb in the DA strain resulted in an earlier disease onset compared with the control group, demonstrating that CD8+ cells regulate arthritis development. In vivo depletion of gammadelta T cells by the V65 MoAb did not alter the disease course, indicating that the disease-suppressive CD8+ cells are alphabeta T cells or NK cells.     

Experimental autoimmune encephalomyelitis in the rat: lessons in T-cell immunology and autoreactivity

Summary: Experimental autoimmune encephalomyelitis (EAE) in the rat is an acute paralytic disease from which most animals spontaneously recover. The disease can be induced in susceptible inbred Lewis and DA rats with myelin basic protein (MBP), or encephalitogenic MBP peptides administered in complete Freund's adjuvant (CFA). The disease can be adoptively transferred to syngeneic recipients with primed T cells that have been reactivated in vitro with antigen. EAE is mediated by CD4⁺ Th1 cells that secrete proinflammatory cytokines, and spontaneous remission is associated with CD4⁺ T cells that secrete transforming growth factor-beta (TGF-β). Studies of EAE in susceptible rats have provided many important insights into the interactions of T cells and accessory cells that culminate in the induction of the autoimmune response.     

Balance of Th1/Th2 Cytokines Associated with the Preventive Effect of Incomplete Freund's Adjuvant on the Development of Adjuvant Arthritis in LEW Rats

Complete Freund's adjuvant (CFA) could induce adjuvant arthritis (AA) in LEW rats and incomplete Freund's adjuvant (IFA) could induce oil induced arthritis (OIA) in DA but not in LEW rats. Lymph node cells (LNCs) from these AA and OIA rats showed increased mRNA expression of IFN-gamma, IL-2 and TNF-alpha but not IL-4. LNCs from IFA immunized LEW rats showed increased expression of IL-4, reduced expression of IFN-gamma and TNF-alpha and no IL-2, in contrast to IFA immunized DA rats. The pretreatment of IFA before CFA challenge could completely prevent AA in LEW rats and their LNCs showed increased expression of IL-4 and IFN-gamma but not IL-2 and TNF-alpha. In F1 (LEW x DA) rats, IFA could not induce OIA but the pretreatment of IFA before CFA challenge could induce very mild AA with 80% incidence, LNCs showing an elevated expression of all the above cytokines. These findings suggest that increased Th1 cytokine expression is associated with disease development and that increased IL-4 expression or the balance of Th2 over Th1 cytokine expression plays an important regulatory role in disease development.     

Polyclonal Th1 cells transfer oil-induced arthritis.

T-cells play a critical role in oil-induced arthritis (OIA) in DA rats. The present study focuses on the involvement of CD4/CD8 T cells in OIA by using adoptive transfer. Mitogen-activated T cells from DA rats previously injected with incomplete Freund's adjuvant (IFA) were depleted of CD4+ T cells or CD8+ T cells before transfer to irradiated naive receipients. The results indicate that CD4+ T cells are essential for the induction of passively induced OIA. However, in vitro blocking experiments with monoclonal antibodies (mAb) to the CD4 molecule of the T cells before transfer did not affect the passive OIA. Neither was passive OIA inhibited by treating the CD4+ T cells with mAb to intracellular adhesion molecule-1 (ICAM-1) in order to block cell-cell interactions or migration. The arthritogenic CD4+ T cells were sensitive, however, to in vitro treatment with mAb to the interleukin-2 receptor, which inhibited the disease or delayed the onset of passive OIA in recipients. The arthritogenic CD4+ T cells were also analysed for expression of specific T-cell receptor (TCR) variable (V) beta chains, critical for recognition of autoantigen, by utilizing V beta gene-specific polymerase chain reaction (PCR). The results show a heterogeneous expression of V beta segments of the TCR, indicating a polyclonal origin of the pathogenic cells. Moreover, an investigation of the T helper (Th)1/Th2 status of the CD4+ T cells, defined by cytokine expression, was made at the mRNA level by using in situ hybridization. High numbers of interleukin-2 (IL-2) mRNA expressing cells and also interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha)-expressing cells could be identified. We conclude from this study that non-immunogenic IFA triggers polyclonal, IL-2-dependent Th1 cells which induce arthritis. The contribution of the CD4 or ICAM-1 molecules for arthritis induction seem to be of minor importance.     

同种异基因移植引流淋巴结及外周血T细胞活化分析

目的:研究同种异基因移植早期局部引流淋巴结和外周血T细胞的活化情况。方法:以小鼠前臂皮下非血管化心肌移植为模型,利用流式细胞术分析前臂引流淋巴结及外周血不同T细胞亚群的CD69表达水平。结果:同种异基因移植后72h,引流淋巴结CD4⁺T细胞和CD8⁺T细胞的CD69表达百分率均明显高于移植前(P＜0.01),且CD8⁺T细胞的表达水平高于CD4⁺T细胞(P＜0.01);各组外周血CD4⁺T细胞和CD8⁺T细胞的CD69表达百分率均无显著差异;局部应用弗氏完全佐剂和全身应用CsA可分别增强和抑制同种异基因移植后CD4⁺T细胞和CD8⁺T细胞的CD69表达(P＜0.05或P＜0.01)。结论:局部引流淋巴结T细胞CD69的表达水平可及时反映受者T细胞对同种异基因抗原的识别情况。     

Dual effects of the alloresponse by Th1 and Th2 cells on acute and chronic rejection of allotransplants

The contribution of direct and indirect alloresponses by CD4⁺ Th1 and Th2 cells in acute and chronic rejection of allogeneic transplants remains unclear. In the present study, we addressed this question using a transplant model in a single MHC class I‐disparate donor–recipient mouse combination. BALB/c‐dm2 (dm2) mutant mice do not express MHC class I L^d molecules and reject acutely L^d+ skin grafts from BALB/c mice. In contrast, BALB/c hearts placed in dm2 mice are permanently accepted in the absence of chronic allograft vasculopathy. In this model, CD4⁺ T cells are activated following recognition of a donor MHC class I determinant, L^d 61–80, presented by MHC Class II A^d molecules on donor and recipient APC. Pre‐transplantation of recipients with L^d 61–80 peptide emulsified in complete Freund's adjuvant induced a Th1 response, which accelerated the rejection of skin allografts, but it had no effect on cardiac transplants. In contrast, induction of a Th2 response to the same peptide abrogated the CD8⁺ cytotoxic T cells response and markedly delayed the rejection of skin allografts while it induced de novo chronic rejection of heart transplants. This shows that Th2 cells activated via indirect allorecognition can exert dual effects on acute and chronic rejection of allogeneic transplants.     

负向调节树突状细胞对心脏移植大鼠调节性T细胞的影响

目的:探讨受者树突状细胞(DC)与体外光化学法(PUVA)处理的供者脾淋巴细胞共培养,对心脏移植受者CD4+CD25+调节性T细胞(Treg)及移植心存活时间的影响。方法:以DA大鼠为供者,Lewis大鼠为受者,SD大鼠为无关供者,建立大鼠腹部异位心脏移植模型。分离正常的供者脾淋巴细胞(SP),制备经PUVA处理的供者脾淋巴细胞(PU-VA-SP)。在体外将DA大鼠PUVA-SP或SP与受者骨髓来源的DC共同培养,收集经上述处理后受者DC,流式细胞术(FCM)检测其表面分子CD80、CD86以及OX6的表达状况。根据受者术前静脉输注的成分将实验动物随机分为3组:①Control组:单纯输注PBS,n=7;②SPDC组:输注加载供者SP的受者大鼠DC,n=8;③PUVA-SPDC组:输注加载PUVA处理的供者SP的受者大鼠DC,n=8。移植术前7d,经外周静脉给受者输注与PUVA-SP共培养后的DC(PUVA-SPDC组)、正常受者DC(DC组)或只输注PBS(Control组),移植术后观察受者移植物的存活时间,检测受者外周血中CD4+CD25+T细胞、CD4+CD25highT细胞的比例及其Foxp3表达状况。过继转移PUVA-SPDC组受者大鼠的T细胞后,检测正常LEW大鼠对供者抗原或无关抗原的DTH反应。结果:受者DC与供者未经处理的脾淋巴细胞(SP)混合培养后,其表面分子CD80、CD86以及OX6的表达分别为16.6%±0.72%、36.5%±0.87%及65.6%±1.45%,明显高于未处理DC组(3.53%±0.27%、13.0%±0.57%及27.7%±1.23%)(P0.01);而受者DC与PUVA处理过的供者脾淋巴细胞(PUVA-SP)混合培养后,其表面分子的表达仍保持较低的水平,CD80、CD86以及OX6的表达分别为3.9%±0.12%、13.4%±0.59%及28.0%±1.73%,与未经任何处理的受者DC无统计学差异(P0.05)。移植术后,PUVA-SPDC组受者,外周血CD4+CD25+T、CD4+CD25highT细胞占CD4+T的比例分别是18.97%和3.81%,明显高于输注DC组(4.40%和0.81%)和Control组(3.11%和0.09%)的大鼠(P0.01)。PUVA-SPDC组大鼠外周血CD4+CD25+T细胞中Foxp3表达率为29%±1.73%,CD4+CD25highT细胞中Foxp3阳性率高达95%±1.67%,均明显高于对照组(12%±0.58%和19.3%±2.03%)及DC(16.3%±0.88%和52.0%±1.73%)组(P0.01)。PUVA-SPDC组大鼠移植心存活时间为(27.3±0.98)d,与Control组(6.7±0.29)d及DC组(11.0±0.32)d相比,明显延长(P0.01)。过继转移实验显示,接受PUVA-SPDC组受者T细胞的正常LEW大鼠对DA大鼠抗原的刺激呈特异性免疫低应答状态。结论:PUVA-SPDC能够在移植受者体内诱生CD4+CD25+Foxp3+Treg,同时诱导抗原特异性免疫低反应,进而延长异基因移植物的存活时间。     

Neutrophils mediate parenchymal tissue necrosis and accelerate the rejection of complete major histocompatibility complex-disparate cardiac allografts in the absence of interferon-gamma

A major feature of acute rejection of cardiac allografts is an intense mononuclear cell infiltration accompanied by interferon (IFN)-gamma production. In the current study we tested the role of IFN-gamma in acute rejection of allografts by comparing the histopathology of rejection in wild-type versus IFN-gamma-/- recipients of major histocompatibility complex-mismatched cardiac grafts. Wild-type recipients rejected the allografts at days 8 to 9 after transplant but rejection was accelerated 2 to 3 days in IFN-gamma-deficient recipients. During rejection in wild-type recipients, the allografts were heavily infiltrated with CD8+ T cells and other mononuclear cells. In contrast, allografts in IFN-gamma-deficient recipients had few T cells but an intense neutrophil infiltration accompanied by extensive graft parenchymal necrosis. No difference in expression levels of neutrophil chemoattractants including Groalpha/KC, MIP-2, GCP-2, and MIP-1alpha, was observed in allografts retrieved from wild-type and IFN-gamma-/- recipients. Depletion of neutrophils from IFN-gamma-deficient recipients delayed rejection until days 8 to 10 after transplant and restored the histopathology of acute allograft rejection to that observed in allografts rejected by wild-type recipients. These results indicate the potent regulatory properties of IFN-gamma during acute rejection directed at neutrophil infiltration into allografts and mediating graft tissue necrosis.     

Pluripotent allospecific CD8+ effector T cells traffic to lung in murine obliterative airway disease

Long-term success in lung transplantation is limited by obliterative bronchiolitis, whereas T cell effector mechanisms in this process remain incompletely understood. Using the mouse heterotopic allogeneic airway transplant model, we studied T cell effector responses during obliterative airways disease (OAD). Allospecific CD8+ IFN-gamma+ T cells were detected in airway allografts, with significant coexpression of TNF-alpha and granzyme B. Therefore, using IFN-gamma as a surrogate marker, we assessed the distribution and kinetics of extragraft allo-specific T cells during OAD. Robust allospecific IFN-gamma was produced by draining the lymph nodes, spleen, and lung mononuclear cells from allograft, but not isograft recipients by Day 14, and significantly decreased by Day 28. Although the majority of allospecific T cells were CD8+, allospecific CD4+ T cells were also detected in these compartments, with each employing distinct allorecognition pathways. An influx of pluripotent CD8+ effector cells with a memory phenotype were detected in the lung during OAD similar to those seen in the allografts and secondary lymphoid tissue. Antibody depletion of CD8+ T cells markedly reduced airway lumen obliteration and fibrosis at Day 28. Together, these data demonstrate that allospecific CD8+ effector T cells play an important role in OAD and traffic to the lung after heterotopic airway transplant, suggesting that the lung is an important immunologic site, and perhaps a reservoir, for effector cells during the rejection process.     

T(h)1 but not T(h)0 cell help is efficient to induce cytotoxic T lymphocytes by immunization with short synthetic peptides

Immunization of BALB/c mice with peptide HVSGHRMAWDMMMNWA, encompassing residues 121-135 from hepatitis C virus E1 protein, induced CD4(+) T(h)1 cells as well as a long-lasting CD8(+) cytotoxic T lymphocyte (CTL) response in vivo when the peptide was administered s.c. with or without incomplete Freund's adjuvant. Using truncated peptides from this sequence it was shown that the determinant recognized by cytotoxic T cells was encompassed by residues SGHRMAWDM. Deletion of residues from the N-terminus or the C-terminus of the wild-type peptide abrogated its helper character. When Val122 of the wild peptide was replaced by Ala, the ability to induce a cytotoxic response was lost concomitantly with the loss of the T(h)1 pattern of cytokine production. Interestingly, the Ala-modified peptide, when co-immunized with a peptide encompassing residues 323-329 from ovalbumin (OVA), which is able to induce a T(h)1 response in BALB/c mice, restored the capacity of the modified peptide to induce CTL. However, co-immunization of the Ala-modified peptide with a peptide encompassing residues 106-118 from sperm whale myoglobin, which induces a T(h)0 cytokine profile in BALB/c mice, was much less efficient than the OVA peptide to restore CTL induction. These results demonstrate that CTL induction with a short synthetic peptide requires that this peptide contains domains recognized by T(c) cells as well as by T(h)1 cells. For those peptides that do not contain this type of T(h) domain, competent T cell help can be provided by co-immunization with a distinct peptide that is able to stimulate a T(h)1 response.     

Allorecognition of HLA-DP by CD4+ T cells is affected by polymorphism in its alpha chain

Alloreactivity to HLA-DP molecules, class II heterodimers of an oligomorphic alpha and a polymorphic beta chain, is increasingly being studied due to its relevance in clinical transplantation. We hypothesized that not only polymorphisms in the peptide binding groove encoded by exon 2 of HLA-DPB1, but also in other regions of the molecule and the alpha chain, could play a role in CD4+ T cell allorecognition. To test this possibility, we comparatively investigated CD4+ T cell allorecognition, measured by upregulation of the activation marker CD137, against HLA-DPB1*13:01, *05:01, *03:01, *17:01 or their allele counter parts DPB1*107:01, *135:01, *104:01, *131:01, with identical exon 2 sequences but polymorphism in exons 1, 3 or 4, in the context of different HLA-DPA1 (DPA1) polymorphisms (DPA1*01:03 and *02:01). No significant differences in CD4+ T cell allorecognition levels could be demonstrated for any of the beyond exon 2 DPB1 variants studied. Interestingly, however, the mean fold change in CD4+ CD137+ cells was significantly higher when the target shared at least one DPA1 allele with the allogeneic stimulator, compared to a distinct DPA1 background (1.65 vs 0.23, P < 0.005). Structural homology modeling suggested specific amino acid residues in the alpha chain, in particular position 31, to impact CD4+ T cell allorecognition of HLA-DP. Our data argue against a significant role of beyond exon 2 DPB1 polymorphisms for T cell alloreactivity, but show relevance of DPA1 polymorphism in this mechanism. These new findings impact HLA matching strategies in unrelated stem cell transplantation.     

Autoantibodies to vimentin cause accelerated rejection of cardiac allografts

Autoimmune responses to vimentin occur after solid organ transplantation, but their pathogenic effects are unclear. The aim of these studies was to investigate the effects of vimentin preimmunization on allogeneic and isografted hearts in a murine transplant model. Immunization of C57BL/6 mice with murine vimentin in complete Freund's adjuvant resulted in anti-vimentin antibodies and vimentin-reactive Th-1 cells. Transplantation of 129/sv hearts into vimentin-immunized C57BL/6 recipients resulted in accelerated rejection (8.4 +/- 1.5 days; n = 18), compared with hen egg lysozyme-immunized C57BL/6 (13.3 +/- 2.2 days; n = 10; P < 0.0001, log-rank test). In contrast, isografts continued to beat beyond 90 days. Immunohistochemical analysis of allografts from vimentin/complete Freund's adjuvant mice demonstrated increased numbers of T cells and enhanced microvascular deposition of C3d, CD41, and P-selectin compared with controls. Antibodies were necessary for accelerated rejection, shown by the fact that vimentin-immunized B-cell-deficient IgH6 mice did not show accelerated rejection of 129/sv allografts, but rejection was restored by adoptive transfer of serum containing anti-vimentin antibodies. Eluates from donor hearts placed in vimentin/complete Freund's adjuvant recipients contained anti-vimentin antibodies, shown by Western blotting. Confocal imaging of rejected hearts de-monstrated presence of vimentin and C3d on apoptosed leukocytes, endothelial cells, and platelet/leukocyte conjugates. These results demonstrate that autoantibodies to vimentin, in conjunction with the alloimmune response, have a pathogenic role in allograft rejection.     

T helper function of CD4+ cells specific for defined epitopes on the acetylcholine receptor in congenic mouse strains.

We previously identified sequence segments of Torpedo acetylcholine receptor (TAChR) alpha subunit recognized by CD4+ cells of congenic mouse strains of different H-2 haplotypes, susceptible to experimental autoimmune myasthenia gravis. CD4+ cells from BALB/c and CB17 mice (H-2d) recognized the peptide sequences alpha 1-20 and alpha 304-322, while C57BL/6 and BALB/b mice (H-2b) recognized alpha 150-169 and alpha 360-378. C57BL/6 mice recognized to a lesser extent also peptide alpha 181-200. In the present study we demonstrate that CD4+ cells which recognize these epitopes have T-helper function. CD4+ cells from TAChR immunized mice, stimulated in vitro with synthetic epitope peptides, induced proliferation in vitro of B cells via soluble factors which were not strain specific, and induced secretion in vitro of anti-AChR antibodies. Upon in vitro stimulation with T-epitope peptides, they secreted interleukin-2. Immunization of mice with synthetic T-epitope peptides caused sensitization of CD4+ cells, which responded in vitro both to the immunizing peptides and to TAChR, and appearance of anti-AChR antibodies in vivo, further identifying the epitope-specific CD4+ cells as AChR-specific T-helper cells.     

胰腺癌高表达抗原MUC4 CTL表位肽的体内免疫原性

目的:检测来源于黏蛋白4(MUC4)的人白细胞抗原(HLA)-A2限制性表位肽免疫BALB/c小鼠后产生细胞免疫应答的水平,筛选出体内具有免疫原性的HLA-A2限制性表位肽。方法:将来源于MUC4的候选HLA-A2限制性表位肽、通用性Th表位和弗氏不完全佐剂联合应用皮下免疫BALB/c小鼠,用酶联免疫斑点实验(ELISPOT)和酶联免疫吸附实验(ELISA)检测小鼠脾细胞表位肽特异性细胞免疫应答的水平,体内细胞毒实验活性检测候选肽诱导细胞毒性T淋巴细胞(cytotoxic lymphocyte,CTL)的能力,并用流式细胞术检测表位肽特异性的CD8+T细胞所占比例。结果:在检测的4个表位肽中,P2004-1Y9V诱导BALB/c小鼠产生的细胞免疫应答最强,细胞毒实验结果显示,P2004和P2004-1Y9V对CAPAN-2细胞均有一定的杀伤作用,且P2004-1Y9V特异性CTLs对CAPAN-2细胞杀伤率高于原肽(P0.05)。胞内因子染色实验进一步表明P2004-1Y9V免疫后可产生特异性的CD8~+T细胞。结论:在来源于MUC4的HLA-A2限制性表位肽中,P2004-1Y9V具有较强的体内免疫原性,可以作为潜在的肿瘤多肽疫苗应用于临床研究。     

Phenotypic and functional analysis of LCMV gp33-41-specific CD8 T cells elicited by multiple peptide immunization in mice revealed the up-regulation of PD-1 expression on antigen-specific CD8 T cells

The phenotype and function of antigen-specific CD8 T cells are closely associated with the efficacy of a therapeutic vaccination. Here we showed that multiple immunizations with LCMV gp33-41 peptide （KAV） in Freund＇s adjuvant could induce KAV-specific CD8 T cells with low expression of CD127 and CD62L molecules. The inhibitory receptor PD-1 was also expressed on a substantial part of KAV-specific CD8 T cells, and its expression level on KAV-specific CD8 T cells in spleen and lymph nodes was much higher when compared to those in peripheral blood. Furthermore, KAV-specific CD8 T cells could specifically kill KAV-pulsed target cells in vivo but the efficiency was low. These data suggest that prime-boost vaccination schedule with peptide in Freund＇s adjuvant can elicit antigen-specific CD8 T cells of effector-like phenotype with partial functional exhaustion, which may only provide short-term protection against the pathogen. Cellular ＆ Molecular Immunology.     

Vaccination with the recombinant Brucella outer membrane protein 31 or a derived 27-amino-acid synthetic peptide elicits a CD4+ T helper 1 response that protects against Brucella melitensis infection

The immunogenicity and protective efficacy of the recombinant 31-kDa outer membrane protein from Brucella melitensis (rOmp31), administered with incomplete Freund's adjuvant, were evaluated in mice. Immunization of BALB/c mice with rOmp31 conferred protection against B. ovis and B. melitensis infection. rOmp31 induced a vigorous immunoglobulin G (IgG) response, with higher IgG1 than IgG2 titers. In addition, spleen cells from rOmp31-immunized mice produced interleukin 2 (IL-2) and gamma interferon, but not IL-10 or IL-4, after in vitro stimulation with rOmp31, suggesting the induction of a T helper 1 (Th1) response. Splenocytes from rOmp31-vaccinated animals also induced a specific cytotoxic-T-lymphocyte activity, which led to the in vitro lysis of Brucella-infected macrophages. In vitro T-cell subset depletion indicated that rOmp31 immunization elicited specific CD4+ T cells that secrete IL-2 and gamma interferon, while CD8+ T cells induced cytotoxic-T-lymphocyte activity. In vivo depletion of T-cell subsets showed that the rOmp31-elicited protection against B. melitensis infection is mediated by CD4+ T cells while the contribution of CD8+ T cells may be limited. We then evaluated the immunogenicity and protective efficacy of a known exposed region from Omp31 on the Brucella membrane, a peptide that contains amino acids 48 to 74 of Omp31. Immunization with the synthetic peptide in adjuvant did not elicit a specific humoral response but elicited a Th1 response mediated by CD4+ T cells. The peptide in adjuvant induced levels of protection similar to those induced by rOmp31 against B. melitensis but less protection than was induced by rOmp31 against B. ovis. Our results indicate that rOmp31 could be a useful candidate for the development of subunit vaccines against B. melitensis and B. ovis.     

Regulatory T cells in experimental allergic encephalomyelitis. III. Comparison of disease resistance in Lewis and Fischer 344 rats

Rats of the Fischer 344 (F344) strain are resistant to experimental allergic encephalomyelitis (EAE) induced by active immunization with guinea pig myelin basic protein (MBP) in complete Freund's adjuvant whereas Lewis (LEW) rats are susceptible even though both strains share the same I-A-like class II alleles of the MHC RT1.B locus. To determine factors that might contribute to this difference in disease susceptibility, we have compared in these two strains (1) the frequency of MBP-reactive T cells in the lymph nodes and spleens of MBP-immunized animals, (2) the dominant MBP epitopes recognized by responding T cells, (3) the ability of MBP-reactive T cells to enter the central nervous system (CNS), and (4) the frequency of CD8+ regulatory T cells (RTC) whose activity is functionally antagonistic to MBP-reactive T cells. The results indicate that MBP-reactive T cell numbers are similar in MBP-immunized F344 and LEW rats, they both recognize p68-88 as the dominant encephalitogenic epitope of MBP, and MBP-reactive T cells isolated from immunized rats and adoptively transferred to naive animals are similarly effective in penetrating the blood-brain barrier and entering the CNS, leading to pathogenesis in EAE. However, the frequency of RTC that functionally inhibit MBP-reactive T cells is greater in F344 rats.     

Synthetic HLA-A2 derived peptides are recognized and presented in renal graft recipients

Indirect presentation of allogeneic MHC antigen is an important pathway by which allografts are rejected and tolerance maintained by regulatory CD4⁺ T cells. In this study HLA-A2 derived synthetic peptides were used to determine whether T cells of non-HLA-A2 renal graft recipients, which had been HLA-A2 mismatched to their organ donors, recognize some of the HLA-A2-derived peptides. Among the HLA-A2 mismatched patients, 60% recognized residues 56–69, 65–79, and 75–89. Peripheral blood lymphocytes derived from healthy individuals showed low reactivity towards allopeptides, indicating that sensitization towards HLA-A2 induced response towards HLA-A2 derived peptides. The response to the peptides was blocked by antibodies to HLA-DR, -DQ, and CD4. Depletion of antigen presenting cells abrogated response towards the allopeptides, confirming that the observed proliferation was mediated by the indirect pathway. Interestingly, although none of the HLA-A2 mismatched patients had any signs for either acute or chronic rejection, considerable response to allo-derived HLA-A2 was observed.     

Arthritis induced in rats with adjuvant oil is a genetically restricted, alpha beta T-cell dependent autoimmune disease.

Adjuvant arthritis in rats is usually induced by injection of mycobacterium tubercle cell walls suspended in various adjuvant oils such as Freund's incomplete adjuvant (FIA) or pristane. We have recently shown that injection of adjuvant oils without inclusion of mycobacterium tubercle cell walls triggers arthritis [oil adjuvant-induced arthritis (OIA)] in the DA rat strain. The OIA is a genetically restricted disease since only DA rats are susceptible while Lewis, DA-fostered Lewis and F1 (Lew x DA) rats are relatively resistant. Activated alpha beta T cells infiltrate the affected joints of adjuvant oil-injected DA rats and treatment with monoclonal antibodies to the alpha beta T-cell receptor abrogates development of arthritis. These findings show that alpha beta T-cell activation is a critical event in the development of OIA.