Induction of suppression following autologous mixed lymphocyte reaction; role of a novel 2H4 antigen

Functional analysis of dendritic cell-T cell interaction in sarcoidosis

The primary cause of the intense immune response in sarcoidosis is unclear. Potentially, a functional abnormality in dendritic cells (DCs) could cause a reduction in clearance of antigen and downstream persistence in immune activity. In this study, we investigate the interaction between monocyte-derived dendritic cells and T cells in patients with sarcoidosis compared to normal controls (n = 8 each) by examining the kinetics of autologous and allogeneic mixed leucocyte reactions over 9-10 days. We found markedly depressed proliferation kinetics in autologous DC-peripheral blood mononuclear cell (PBMC) co-cultures from sarcoid patients compared to normal subjects. In allogeneic experiments PBMCs from patients showed a reduced response to allogeneic DCs from a single donor, but no difference was observed in the ability of patients and control DCs to stimulate proliferation of allogeneic PBMC from a single donor. We conclude that there is a markedly impaired autologous mixed leucocyte reaction (MLR) in sarcoidosis patients. In allogeneic MLR, monocyte-derived DCs in sarcoidosis were able to stimulate T cells normally, but PBMCs responses were reduced. This contradicts recent published studies on ex vivo isolated myeloid DCs from sarcoidosis patients although, potentially, an in vivo conditioning factor, which reduces DC function in sarcoidosis, could be a unifying explanation for the contrasting findings.

Adoptively transferable tolerance induced by CD45RB monoclonal antibody

The phenomenon of rejection remains the most serious problem in transplantation. The ultimate goal in transplant immunology is to develop therapeutic strategies that lead to tolerance. It has been shown that two injections of a monoclonal antibody to CD45RB leads to indefinite acceptance of renal allografts in mice. Moreover, the CD45RB monoclonal antibody reverses acute rejection and still induces tolerance. The purpose of this study was to assess mechanisms that could underlie this therapeutic benefit. It was shown that splenic lymphocytes from tolerant animals augmented proliferation in allogeneic mixed lymphocyte reactions against donor alloantigens, and the serum of tolerant mice contained donor-specific antibodies, mainly of the IgG1 isotype, suggesting the presence of TH2 cytokines. Tolerance could not be broken by interleukin-2 infusion, but tolerance could be adoptively transferred by transfusion of tolerant mouse CD4+ splenic lymphocytes into naive allografted animals. These data suggest that an active immunoregulatory mechanism is partly responsible for the therapeutic effect. CD45RB-directed therapy may find clinical application in organ transplantation in human patients.

Initiation of the Autologous Mixed Lymphocyte Reaction Requires the Expression of Costimulatory Molecules B7-1 and B7-2 on Human Peripheral Blood Dendritic Cells

The human autologous mixed lymphocyte reaction (AMLR) consists of a proliferative response of primarily CD4+ T lymphocytes stimulated by autologous non-T cells expressing class II MHC-encoded gene products and is thought to represent a self-recognitive mechanism that might be important in regulating the cellular interactions involved in the generation of normal immune responses. To further define appropriate stimulator cell populations, as well as the molecular mechanism responsible for the initiation of AMLR, we compared the T cell-stimulatory capacity of highly purified populations of peripheral blood dendritic cells (DCs) and monocytes (Mos) under serum-free conditions, thus carefully avoiding the presence of xenogeneic Ags. Whereas both freshly isolated Mos and DCs were found to be poor stimulators of autologous T cell proliferation, preactivation of DCs, but not of Mos, for 48 h with granulocyte-macrophage CSF led to a 113-fold increase in DC stimulatory capacity. AMLR was inhibited by mAbs against HLA-DR and CD4 molecules, and, in addition, showed a higher dependence on the granulocyte-macrophage CSF-induced up-regulation and/or de novo expression of the costimulatory molecules B7-2 and, in particular, B7-1 as compared with an Ag-specific or allogeneic MLR. Thus, our data suggest that the high density of costimulatory molecules together with MHC class II molecules on competent APCs appear to be the major triggers for the initiation of AMLR.

Interactions between non-immune host cells and the immune system during periodontal disease: role of the gingival keratinocyte

Periodontal disease and inflammatory dermatoses, such as psoriasis, are characterized by the accumulation of dense inflammatory infiltrates immediately beneath the epithelial cell layer of the gingiva and skin, respectively. Dermatologists are increasingly aware that the epidermal keratinocyte probably contributes to inflammatory disease progression by secreting a number of pro-inflammatory cytokines and expressing various adhesion molecules. In psoriatic lesions, it is now believed that epidermal keratinocytes may also act as antigen-presenting cells and participate directly in the superantigenic activation of T-cell clones, some of which may initiate, contribute to, or maintain the disease process. Although the role of the host response in periodontal disease has been extensively studied over the years, very little is known about the contribution of the gingival keratinocyte to the inflammatory response. The available published information is discussed in this review, and we suggest that, like its epidermal counterpart, the gingival keratinocyte may participate actively in the pathogenesis of periodontal disease.

Senescence-related change in autologous mixed-lymphocyte reaction in senescence-accelerated mice

Using the senescence-accelerated mouse (SAM) strains, we examined the senescence-related changes of autologous mixed-lymphocyte reaction (AMLR) as well as the phenotypic alteration of the T cell subsets. Splenic T cells from senescence-prone (SAM-P) and resistant (SAM-R) strains of mice were incubated with autologous non-T cells, and AMLR was measured on day 1-5. The kinetics of AMLR responses revealed a marked alteration in senescent SAM-P but not in non-senescent SAM-R mice, in which the peak response occurred at day 1, the response decreasing thereafter up to day 5. Similar senescence-related change was observed in aged (24-month-old) SAM-R and BALB/c mice. Furthermore, the T cells from the aged SAM-R mice cultured with non-senescent syngeneic non-T cells showed a very similar pattern to that cultured with autologous non-T cells. Flow cytometric analysis of T cell phenotype indicated that the percentage of CD4+ CD45RBhi T cells correlated with the peak AMLR responses in both SAM-P and SAM-R mice, and that the percentage of the T cell subset with extrathymic properties was significantly higher in SAM-P mice. These findings suggest that the alteration in kinetics of AMLR is related to senescence but not to the strain of mice, and may reflect a senescence-related dysfunction of the autoregulatory immune mechanisms of T cells.

Indefinite islet allograft survival in mice after a short course of treatment with anti-CD45 monoclonal antibodies

BACKGROUND

Although islet cell transplantation is considered an ideal form of endocrine replacement for type I diabetes, clinical application in humans is still not feasible. New immunosuppressive strategies are clearly needed to control inexorable rejection. CD45 is a family of transmembrane protein tyrosine phosphatases critically involved in the regulation of lymphocyte activation signals. Anti-CD45RB monoclonal antibody can prevent rejection of murine renal allografts.

METHODS

Here, we examine the consequences of targeting CD45 in murine islet cell transplantation. Diabetic mice recipients received islet allografts under the kidney capsule and were divided into seven groups. Recipients received no treatment (controls) or anti-CD45RB monoclonal antibody (mAb; MB23G2 or C363.16A) at different dosages and treatment intervals.

RESULTS

All untreated control animals lost islet function, becoming hyperglycemic within 10-17 days after transplantation. Animals treated with either anti-CD45RB mAb showed a significant prolongation of islet allograft survival when compared with controls. Anti-CD45RB MB23G2 at 100 microg/day, given on days -1, 0, and 5 was particularly effective, inducing indefinite islet allograft survival in 60% of recipients.

CONCLUSIONS

These results indicate that anti-CD45 mAbs are potent immunomodulatory agents, able to sustain indefinite islet allograft function after a short treatment course in the highly immunogenic model of islet transplantation.

Generalized prepubertal periodontitis. A report of 4 cases with the immunological findings

The clinical and immunological data from 4 patients with generalized prepubertal periodontitis are presented. The peripheral blood neutrophil chemotaxis was measured using zymosan activated sera as the chemoattractant. All of the 4 patients have shown depressed neutrophil chemotaxis compared to those of the healthy controls. Peripheral blood lymphocyte subpopulations were analysed by double-coloured flow cytometry using monoclonal antibodies for the receptors CD2, CD3, CD4, CD8, CD19, CD29, CD45RA+, 34,29dK, CD56. CD11b/CD18. Lymphocytes bearing CD3 receptors showed a significant decrease compared to those of the controls. Natural killer cells were lowered in 3 of the 4 cases. All of the patients showed a higher increase in CD11b/CD18 expression. The evaluation of CD11b/CD18 receptor in peripheral blood leukocytes may be of help explaining the rôle of neutrophils in the pathogenesis of the disease.

Cell-type specificity of anti-CD45 autoantibodies in systemic lupus erythematosus

OBJECTIVE

To determine the specificity of anti-CD45 autoantibodies in systemic lupus erythematosus (SLE) for native CD45 and for CD45 expressed by T cells and B cells, and at different stages of cellular activation.

METHODS

CD45 purified from different types of lymphocytes was examined by immunoblotting with sera from patients with SLE. Indirect immunofluorescence experiments were performed with purified anti-CD45 autoantibodies.

RESULTS

IgM anti-CD45 autoantibodies in SLE recognize native CD45 expressed on the surface membrane of viable lymphocytes and CD45 purified from activated peripheral T cells and certain T cell lines, but not CD45 purified from B cells or resting peripheral T cells. The presence or absence of reactivity is independent of the individual isoforms expressed.

CONCLUSION

Recognition of CD45 by IgM antilymphocyte autoantibodies in SLE varies with the lineage and state of activation of the lymphocyte target. This pattern of reactivity is consistent with autoantibody specificities involving CD45 glycoforms, rather than CD45 isoforms.

Cyclophosphamide plus tumor necrosis factor-alpha chemoimmunotherapy cured mice: life-long immunity and rejection of re-implanted primary lymphoma

Changes in functionally and phenotypically definable splenocyte subsets in aging mice which had been rendered tumor-free in early life by immunochemotherapy (cyclophosphamide plus tumor necrosis factor-alpha) were studied in the syngeneic EL4 lymphoma-C57BL/6 murine model. Treatment-induced long-term survivors (LTS) surviving rechallenge are termed "immune-LTS". On day 120 (day 0, initial tumor inoculation), splenocytes from day 60 rechallenged immune-LTS developed significantly greater specific anti-EL4 cytolytic activity in an ex vitro assay than those from non-rechallenged LTS. Splenocytes from combination-treated groups developed significantly higher activity than those from cyclophosphamide-induced immune-LTS. The splenic effector precursor was a CD8+ T cell. The specific anti-EL4 effector cell from the cyclophosphamide-induced immune-LTS was CD4- CD8+; however, approximately 50% of those from combination-treated immune-LTS appeared to be CD4+CD8+. On day 520 immune-LTS were randomized into 2 groups. One group was re-implanted with EL4 tumor; all mice survived. The other group was killed and, even though their splenocytes developed considerable anti-EL4 activity, their allogeneic responsiveness was as reduced as that of age-matched controls. Phenotypic analysis, compared with splenocytes from young and age-matched controls, revealed changes in the makeup of each T-cell subset, except the CD4+CD8+, and all subsets, except the CD4-CD8-, had increases in CD44 positivity. On day 625, the age of these mice was equivalent to the median life-span of C57BL/6 mice; nevertheless, their splenocytes developed high anti-EL4 activity. Phenotypic analysis indicated that, compared to day 520, there was a major decrease in CD4-CD8+ splenocytes; we suggest that these cells had migrated to the site of tumor eradication.

Reduced CD8+ peripheral blood T lymphocytes in rapidly progressive periodontitis

The peripheral blood T-cell phenotype of patients with rapidly progressive periodontitis (RPP) was determined in order to investigate whether there were T-cell imbalances or not. Twenty patients aged 21-39 yr were selected for this study. Bone resorption and probing pocket depth were measured. All the patients had 10 or more teeth showing bone loss of 50% or more. As controls, 12 periodontally healthy, age-matched individuals were selected. Blood samples were obtained by venipuncture, and lymphocytes were isolated. Two-colour flow cytometric analysis was done with monoclonal antibodies against human CD4, CD8, and CD45RA antigens. The RPP patients were found to have significantly lower percentage of CD8+ T cells (Mann-Whitney's U-test, p < 0.01) and an increased CD4/CD8 ratio (Mann-Whitney's U-test, p < 0.01) compared with healthy individuals. On the other hand, there were no significant differences in the percentages of CD4+ T cells and CD4+ CD45RA+ T cells between RPP patients and healthy individuals. No correlations between the clinical findings and T-cell subsets were found. These findings suggest that imbalances of peripheral blood T lymphocytes, especially a tendency to decreased CD8 + T cells, exist in RPP patients, and that cellular immune responses mediated by CD8 + T cells may play a part in the pathogenesis of RPP.

Induction of peptide-specific primary cytotoxic T lymphocyte responses from human peripheral blood

Various protocols were developed and compared for eliciting specific cytotoxic T lymphocyte (CTL) cell lines from the unselected human peripheral blood mononuclear cells of naive donors. Interleukin-7 and CD4+ T cells primed in vitro by keyhole limpet hemocyanin were shown to act together in the generation of these responses. Primary responses were consistently induced with a variety of different HLA class I-binding malarial peptides. Primary CTL responses could be induced from unselected CD8+ and from CD45RA+CD8+ T cells. The CTL lines derived from these naive donors were CD8+ and demonstrated a high level of HLA class I-restricted killing for > 3 months after priming in vitro. They were also able to recognize and kill targets infected with a recombinant vaccinia virus containing the full-length antigen. In addition, this same protocol enhanced up to fourfold the levels of secondary CTL responses induced. The optimal method presented for naive cytotoxic T cell stimulation is simple, rapid and generally applicable and should provide a useful tool for both basic research and human therapy.

Neonatal injections of cyclosporin enhance autoimmune diabetes in non-obese diabetic mice

Since the modulation of the immune system at birth may influence the course of insulin-dependent (type 1) diabetes, we investigated whether neonatal injections of cyclosporin (CsA) to newborn non-obese diabetic (NOD) mice influence diabetes during later life. Two groups of 90 mice (45 female, 45 male) were injected intraperitoneally for the first 6 days of life with CsA (10 mg/kg per day) or with vehicle. In female NOD mice, the onset of diabetes was earlier and cumulative incidence was higher after neonatal treatment with CsA (P < 0.01). The incidence of diabetes was also dramatically enhanced in male NOD mice (P < 0.01), which normally display a very low disease incidence. Concomitantly, the severity of lymphocytic infiltration of the pancreatic islets was higher in female NOD mice neonatally treated by CsA (P < 0.02), and to a lesser extent in males, than in control mice. After administration of CsA to newborn NOD mice, there was a reduction (P < 0.01) of both CD4+CD8- and CD4-CD8+ thymocytes, whereas the number of double positive CD4+CD8+ thymocytes was increased. Concomitantly, Thy1-2+ cells in spleen were decreased (P < 0.01), and spleen cells expressing either CD3 molecule or alpha beta TCR complex were diminished (P < 0.01). Both CD4+ and CD8+ spleen T cells were depleted. By contrast, the low percentage of gamma delta TCR-expressing splenocytes was not modified. Numbers of MHC class 1+ or MHC class 2+ spleen cells were also depressed (P < 0.01). After neonatal injections of CsA, spleen cells showed a reduced response to concanavalin A (Con A) (P < 0.01). On the contrary, stimulation indices of splenocytes incubated with xenogeneic insulin-producing cell extracts were enhanced (P < 0.03). Proliferation indices of splenocytes to self class 2 antigens, generating suppressor cell activity, during syngeneic mixed lymphocyte reaction (SMLR) were significantly reduced (P < 0.01). Irradiated NOD mice were used as recipients for spleen cells from CsA-neonatally treated NOD mice. They displayed enhanced insulitis 2 weeks after transfer, and diabetes was successfully produced by 1 month after transfer in 50% of the recipients. By contrast, NOD mice which received control syngeneic spleen cells remained normoglycaemic, with only moderate islet infiltration which would be expected of NOD mice of this age. Thus, neonatal injections of CsA markedly enhance diabetes in both female and male NOD mice.(ABSTRACT TRUNCATED AT 400 WORDS)

The apoptosis-1/Fas protein in human systemic lupus erythematosus

Three independent mutations involving the apoptosis-1 (APO-1)/Fas receptor or its putative ligand have led to lupuslike diseases associated with lymphadenopathy in different strains of mice. To determine whether humans with SLE also have a defect in this apotosis pathway, we analyzed the expression of APO-1 on freshly isolated blood mononuclear cells and on lymphocytes activated in vitro using flow cytometry and the monoclonal antibody anti-APO-1. Significantly higher level of APO-1 expression were detected on freshly isolated peripheral B cells and both CD4+ and CD8+ T lymphocyte populations obtained from lupus patients when compared with normal controls (P < 0.001). Almost 90% of the cells that stained positive for APO-1 also expressed the CD29 antigen, suggesting that APO-1 was upregulated after lymphocyte activation in vivo. No defect in APO-1 regulation was detected after activation of SLE T (with anti-CD3) or B (with Staphylococcus aureus Cowan 1) lymphocytes in the presence of IL-2 in vitro. Similarly, the anti-APO-1 antibody induced apoptosis in 74 +/- 5% of activated SLE T cells in vitro compared with 79 +/- 6% of the normal controls (P > 0.05). These results reveal that, while APO-1/Fas may play an important role in the regulation of lymphocyte survival in SLE, no consistent defect in the expression or function of the receptor could be detected in these studies.

Modulation of suppressor cell activities by cyclophosphamide in breast cancer patients

We investigated the immunomodulatory effect of cyclophosphamide on the induction of suppressor cell activities in peripheral blood lymphocytes. The sera from advanced breast cancer patients as well as concanavalin-A (Con-A) induced suppressor cell activities in lymphocytes from healthy volunteers. Pretreatment of these lymphocytes, including CD4+ T cells with 4-hydroperoxycyclophosphamide (4-HC), an active form of cyclophosphamide, abrogated the induction of suppressor cell activities by either cancer sera or Con-A. A decrease in CD4+CD45RA+ suppressor/inducer T cells and reduction of Con-A induced suppressor cell activities were observed in breast cancer patients with metastases that were treated with cyclophosphamide (CPM). These results suggest that cyclophosphamide may modulate the immune responses of breast cancer patients by interference with suppressor/inducer T cells.

Carbohydrate specificity of IgM autoantibodies to CD45 in systemic lupus erythematosus

Patients with SLE develop IgM autoantibodies to different isoforms of CD45, the major surface membrane protein tyrosine phosphatase on lymphocytes and other nucleated hemopoietic cells. Because such autoantibodies could have a potential role in the development of immune dysfunction in this disorder, we performed a series of experiments to characterize their antigenic specificity further. Blots of recombinant E. coli fusion proteins encoded by exons 3-7 of the p220 and p180 isoforms were uniformly non-reactive with SLE IgM, suggesting that anti-CD45 autoantibodies in SLE are directed against conformational and/or carbohydrate epitopes, rather than linear polypeptide epitopes. This issue was examined further using chemically and enzymatically modified CD45 purified from T cells by lectin affinity chromatography as substrates. Treatment of CD45 with 25 mM sodium-m-periodate, sufficient to abrogate binding to various lectins, abolished the reactivity with SLE anti-CD45 autoantibodies. On the other hand, digestion of CD45 with neuraminidase enhanced the binding of anti-CD45 autoantibodies from some of the SLE sera. This result probably reflects decreased steric hindrance or charge repulsion because the binding of mouse monoclonal antibodies directed against linear polypeptide epitopes of CD45 was similarly enhanced. Digestion of CD45 with N-glycosidase F had no effect on autoantibody staining. Taken together, these data suggest that IgM anti-CD45 autoantibodies in SLE recognize non-sialylated carbohydrate determinants in the highly O-glycosylated polymorphic domains of CD45.

Upregulated expression and function of integrin adhesive receptors in systemic lupus erythematosus patients with vasculitis

Upregulation of integrin adhesive receptors has been implicated in various pathological conditions. We examined expression and function of integrin adhesive receptors on peripheral blood lymphocytes from patients with systemic lupus erythematosus (SLE), particularly those with the complication of vasculitis, and found that VLA-4 and LFA-1 expression was increased in SLE patients with vasculitis, while LFA-1 but not VLA-4 expression was increased in those without vasculitis. These results suggested a role of VLA-4 in the pathogenesis of vasculitis in SLE. Functional studies further demonstrated that adhesion to cytokine-activated human umbilical cord vein endothelial cells and to the CS-1 alternatively spliced domain of fibronectin was significantly increased in SLE patients with vasculitis. Analysis of the functional epitopes on the alpha 4 chain demonstrated that antigen densities of all the functional epitopes were increased in those with vasculitis, indicating that the increased expression of VLA-4 resulted from the increased number of VLA-4 molecules, and was not secondary to an increase in one particular functional epitope. Immunoprecipitation studies further support these results. Interestingly, high molecular weight bands associated with VLA-4 were observed in about half of the SLE patients with vasculitis. These results introduce a possibility that upregulation of integrin adhesive receptors has a potential role in the pathogenesis of vasculitis in SLE.

Immunohistological analysis of memory T lymphocytes and activated B lymphocytes in tissues with periodontal disease

Memory T-cells and activated B-cells were identified in cryostat sections of adult periodontitis (AP) lesions and categorized in terms of frequency and distribution. Nineteen periodontitis biopsies were obtained at the time of periodontal surgery to remove residual periodontal pockets following the completion of initial preparation. Gingival tissues exhibited various degree of inflammation (GI of 0-2) but probing depths of > 4 mm and > 5 mm loss of attachment. As a control, 5 gingivitis specimens (GI of 1, probing depth and loss of attachment of < or = 3 mm) were obtained from premolar and third molar sites requiring extraction for either orthodontic treatment or pericoronitis. Serial cryostat sections (6 microns in thickness) were prepared from each biopsy, on which a double staining avidin-biotin immunoperoxidase and avidin-biotin alkaline phosphatase technique was used to identify CD4+, CD45RO+ memory T-cells and activated CD19+ B-cells expressing CD23 or CD25. In periodontitis lesions, the mean percentage of CD4+ cells expressing CD45RO was consistently high (65.9% in the crevicular (C) one-third (1/3), 61.2% in the middle (M) 1/3 and 62.5% in the oral (O) 1/3). This contrasts with the low mean percentage of CD4+, CD45RA+ naive T-cells (17.1% in the C 1/3, 14.8% in the M 1/3 and 12.4% in the O 1/3). In gingivitis specimens, the incidence of CD4+, CD45RO+ was 81.9% in the C 1/3, 81.1% in the M 1/3 and 89.0% in the O 1/3. This was higher than that of periodontitis biopsies. With CD4+, CD45RA+ the incidence was 10.0% in the C 1/3, 8.0% in the M 1/3, and 6.6% in the O 1/3 and the relationship to the periodontitis biopsies was reversed. However, the percentage of CD23+ and CD25+, CD19+ B-cells which were identified in 13 out of 19 samples from periodontitis varied significantly (0-100% for CD23, 0-36.2% for CD25) in spite of similar clinical status. The frequency of B-cells and activated B-cells in the gingivitis was much lower than that of periodontitis. These results indicate that both T-cells and B-cells were in active stage in periodontitis lesions. Differences of immunohistological features between gingivitis and periodontitis may be attributable to the heterogeneity of profiles of cytokine production by CD4+, CD45RO+ "memory' cells.

Regulatory role of OX22high T cells in mercury-induced autoimmunity in the brown Norway rat

The monoclonal antibody OX22 defines a functional split within CD4+ T cells in the rat, with OX22high cells mainly producing interleukin 2 (IL-2) and interferon gamma and responsible for delayed-type hypersensitivity responses, and OX22low cells mainly producing IL-4 and -5 and responsible for providing B cell help. There are reciprocal interactions between OX22high and OX22low cells, and it has been suggested that the OX22low subset has a role in the prevention of autoimmunity. We have used OX22 in vivo to define the role of these subsets in mercuric chloride-induced autoimmunity in the Brown Norway rat. In this model, there is polyclonal B cell activation and animals develop widespread tissue injury. Treatment of thymectomized animals with OX22 led to a profound reduction in the number of OX22high T cells in the peripheral blood. OX22-treated animals consistently developed more severe tissue injury than controls given an irrelevant antibody of the same isotype. Control animals pretreated with broad spectrum antimicrobial drugs showed milder tissue injury, but this protective effect of antimicrobials was lost in OX22-treated animals. Transfer of naive T cells to OX22-treated animals provided protection, but if T cells were depleted in vitro of OX22high cells before transfer, this effect was lost. These data provide evidence for a protective immunoregulatory role for OX22high T cells in mercuric chloride-induced autoimmunity.

Early phenotypic activation of circulating helper memory T cells in scleroderma: correlation with disease activity

OBJECTIVES

The differential expression of several accessory/activation molecules (CD26, CD29, CD45RA, CD25, MLR4, HLA-DR) on peripheral blood CD4+ and CD8+ T lymphocytes in patients with scleroderma was compared with that in controls and patients with other connective systemic diseases to look for evidence of the involvement of T cells in the disease process of scleroderma.

METHODS

The two colour expression of surface molecules by circulating T cells was analysed with a panel of monoclonal antibodies and flow cytometry in 17 patients with scleroderma, 10 patients with systemic lupus erythematosus, and five patients with rheumatoid arthritis, and the results compared with those for 10 normal controls. The two colour T CD4+ phenotype was further compared between patients with active and quiescent disease in these patients with scleroderma. The coexpression of surface molecules by CD4+ T cells was also analysed by three colour flow cytometry in eight patients with scleroderma.

RESULTS

Patients with scleroderma showed increased CD4+CD26+ and CD4+CD25+ percentages and absolute numbers and decreased CD8+CD29+ percentages compared with controls. Moreover, a significant correlation between the higher CD4+CD26+ T cell percentage and absolute cell numbers with disease activity was observed. Most of the CD4+ peripheral blood T cells from patients with scleroderma showed the CD26+CD45RA- phenotype by three colour flow cytometry analysis.

CONCLUSIONS

The distinctive pattern of early helper memory T cell activation in these patients with rapidly evolving scleroderma supports the role of a T cell mediated mechanism in the progression of scleroderma.

Ro/SSA inhibits the autologous mixed lymphocyte reaction

To test the hypothesis that the Ro/SSA autoantigen can be recognized as antigenic by the human immune system, lymphocytes obtained from normal volunteers were used in in vitro assays evaluating the ability of Ro/SSA (mol. wt 60 kD) to induce B and/or T cell responses. Bovine Ro/SSA strongly inhibited the autologous mixed lymphocyte reaction in a dose-dependent manner without similar effects on concurrently performed allogeneic mixed lymphocyte reactions or T cell proliferation induced by phytohaemagglutinin. Using three colour FACS analysis, Ro/SSA was found to decrease the percentage of CD4+CD45+RA+ T cells in the proliferative, S+(G2+M), phase of the cell cycle. Associated with the decrease in the percentage of suppressor-inducer cells, was the finding that Ro/SSA was able to augment RF production in pokeweed mitogen stimulated cultures of peripheral blood lymphocytes.

Phenotypic and functional analysis of peripheral blood lymphocytes in oral lichen planus

To assess cellular immunity in oral lichen planus (OLP), peripheral blood mononuclear cells (PBMC) were obtained from 19 OLP patients and 30 control subjects. The proportions of circulating CD45RA+ and CD29+ lymphocyte subsets were determined. The proliferative activity of PBMC to the non-specific plant mitogens phytohemagglutinin (PHA) and concanavalin A (Con A) was examined together with the spontaneous proliferative response and the response in the autologous mixed lymphocyte reaction (AMLR). In the OLP group, the proportion of CD4+ CD45RA+ T lymphocytes was significantly less than control subjects and the proportion of CD4+ CD29+ T lymphocytes was increased significantly. The proliferative response to PHA was similar in OLP and controls subjects. Con A-stimulated PBMC proliferation was decreased significantly in the OLP group. Spontaneous PBMC proliferation in patients with non-reticular lesions was significantly less than control subjects. Despite a mildly depressed response in the AMLR in OLP patients, this result was not statistically significant. Results of the phenotypic analysis of peripheral blood lymphocytes indicate a decreased proportion of naive T cells and an increased proportion of primed memory T cells, although the antigen specificity of these memory cells remains to be determined. Results of the functional assays would seem to reflect this phenotypic shift, and as T cells responding to Con A stimulation and in the AMLR possess suppressor-inducer activity, these results may also suggest an association between OLP and defective innate T cell-mediated suppressor circuits.

Activation of T cells through a T cell-specific epitope of CD45

The 180- and 190-kDa isoforms of CD45 are preferentially expressed on the helper inducer (memory) subset of CD4 cells. In order to generate monoclonal antibodies against the extracellular domains of these isoforms and determine whether they could regulate the function and activation of these cells, we developed a mAb, anti-4H2D, by immunizing Balb/c mice with an isogenic mouse pre-B cell line expressing the human 190-kDa CD45 isoform. Anti-4H2D reacts with approximately 60% of T cells, 70% of CD4 cells, and 60% of CD8 cells. The CD4 cell population defined by this mAb corresponds functionally and phenotypically to that defined by the CD45RO+CD29+ subset. Western blotting demonstrated that anti-4H2D reacts primarily with the 190-kDa isoform of CD45 and to a minor extent, the 205- and 180-kDa CD45 isoforms. Interestingly, this mAb reacted with only a subpopulation of mature thymocytes and peripheral T cells, despite the fact that the 190-kDa CD45 isoform, as well as CD45RO and CD29, is more widely distributed on cells of hematopoietic origin. The 4H2D epitope was neuraminidase sensitive, indicating that anti-4H2D reacts with a carbohydrate epitope which is present on only a subset of the T cells containing the 190-kDa CD45 isoform epitopes. Functional studies showed that soluble anti-4H2D augmented T cell proliferation induced by the CD2 and CD3 pathways, and treatment of T cells with this mAb up-regulated [Ca2+]i flux induced by both anti-CD2 and anti-CD3 mAbs. These results suggest that the 190-kDa CD45 isoform on human CD4 cells is heterogeneous and that the 190-kDa isoform recognized by anti-4H2D regulates the function and activation of CD4 helper T cells.

Activation of human CD4+CD45RA+ T cells by chrysotile asbestos in vitro

Chrysotile asbestos stimulates T lymphocyte subsets. Cell surface CD4 or CD45RA expression in peripheral blood mononuclear cells (PBMC) was downregulated after incubation with chrysotile asbestos in vitro temporarily. The percentage of CD4+CD45RA+ cells and mean fluorescence intensity in CD4 or CD45RA decreased after incubation with asbestos and returned to the original level after 24 h of incubation, which suggests that chrysotile asbestos activates CD4+CD45RA+ cells. No change was observed in CD29 expression. An increased percentage of IL-2R positive cells and an elevated intracellular Ca++ level were also indicative of the activation of PBMC by chrysotile asbestos.

Differential effect of dipyridamole upon thymidine incorporation and expression of surface activation antigens by in vitro stimulated lymphocytes

Dipyridamole inhibits, by 50% at 10(-6) M and 100% at 10(-5) M, the incorporation of tritiated thymidine by lymphocytes stimulated with 1 microgram/ml phytohaemagglutinin A for 72 h. At the latter concentration, a clinically relevant one, dipyridamole fails to inhibit lymphocyte proliferation and expression of the cell surface stimulation markers, CD25 and HLA-DR, or differential regulation of the CD45 -RA and -RO isoforms, as determined by single laser two-colour flow-cytometry. No significant immunodepressant effect of dipyridamole can be demonstrated in vitro.

Multiparametric flow cytometric analysis of the kinetics of surface molecule expression after polyclonal activation of human peripheral blood T lymphocytes

In this report we have analysed the kinetics of modulation of human peripheral blood T lymphocyte membrane molecules upon activation with optimal amounts of phytohaemagglutinin (PHA) and concanavalin A (ConA). The following activation-related and differentiation/adhesion molecules were selectively and concomitantly investigated on CD4+ and CD8+ subsets by dual colour flow cytometry: CD69, CD25 and CD71; CD2, CD45RA and L-selectin. Cultures were assayed after 24, 48, 72, 120 and 168 h of incubation with PHA and ConA. This approach allowed a comprehensive evaluation of membrane phenomena occurring during activation of normal resting human T lymphocytes. Data show that the kinetics of expression of these molecules follows a precise and consistent time-course with no major differences between CD4 and CD8 subsets. CD69 expression peaked at 24 h, whereas CD25 and CD71 expression peaked at 48/72 h with some differences between PHA and ConA activation. L-selectin expression started an evident decrease in step with culture time whose magnitude was dependent on the lectin used, being higher with PHA than with ConA. Conversely, the expression of CD45RA remained stable for 72 h and then briskly decreased with no major differences between PHA and ConA activation. CD2 molecules increased with time in number and density, although the percentage of positive cells remained essentially constant (greater than 85%). After 48/72 h of stimulation about 10% of cells co-expressed CD4 and CD8 molecules. To ascertain whether the phenomenon was restricted to cells in a particular activation state, the phenotype of cells in the diverse phases of the cell cycle was established. Results obtained show that only actively proliferating cells, that is cells in S and G2-M phases, co-expressed the two molecules, suggesting that such a phenomenon reflects a momentary dysregulation of the normal sequence of gene expression. The present data are also discussed in the light of the dynamic role of T lymphocyte activation and adhesion molecules in regulating cell-cell interactions, tissue localization and eventual immunological function.

Ovine lentivirus is macrophagetropic and does not replicate productively in T lymphocytes

The lentiviruses of sheep, goats, and horses cause chronic multiorgan disease in which macrophages are highly permissive for viral replication. Monocytes, which mature into macrophages, are thought to be latently infected with lentivirus, but the extent to which other leukocytes are infected is unknown. Dendritic cells have not been studied separately from monocytes and T-cell subsets have not been examined in previous attempts to identify infected cells in peripheral blood mononuclear cells (PBMC). We found no evidence of T-cell tropism using an animal-passaged, pathogenic ovine lentivirus. Phytohemagglutinin-stimulated infectious PBMC produced 20-fold less virus than differentiated macrophages, and cocultivation of infectious PBMC with fresh, uninfected phytohemagglutinin blasts did not facilitate virus replication. Furthermore, central lymph cells, the best in vivo source of purified lymphocytes, lacked virus and did not yield virus upon in vitro cultivation. In contrast, cultivated blood-derived macrophages were highly permissive for viral replication. To identify the latently infected PBMC, PBMC from infected sheep were selectively depleted of monocytes and B cells by passage over nylon wool and then of nonadherent cells bearing CD4, CD8, T19, gamma delta T-cell receptor, CD45RA, or major histocompatibility complex class II antigens by panning. Removal of adherent monocytes and B cells or of adherent cells and the three major T-cell subsets (CD4+, CD8+, T19+) did not decrease the infectivity of PBMC. The richest sources of infected cells in fresh PBMC were CD45RA+ and major histocompatibility complex class II+ nonadherent cells, which are three characteristics of dendritic cells. Thus, the dendritic cell, and not the monocyte or the CD4+ cell, is probably the predominant infected cell type in blood.

CD4+ CD45RA+ T cells modulate allergen-induced interleukin 2 responsiveness in human lymphocytes

Peripheral blood lymphocytes from nonallergic individuals acquired responsiveness to interleukin 2 (IL2) after stimulation with ovalbumin (OVA) or Dermatophagoides farinae (Df) antigens when they were pretreated with the CD45RA antibody, which has been shown to define the suppressor inducer subset of CD4+ cells and also to block its suppressor activity. The effect provided by the CD45RA antibody was lost if the lymphocytes had initially been activated with the OVA of Df antigens. The magnitude of the responses was comparable to the allergen-induced responses observed in OVA- or Df-sensitized lymphocytes from allergic patients. The pre-existing IL2 responsiveness in the patients was not increased by the CD45RA antibody pretreatment. However, the CD45RA antibody pretreatment gave rise to Df-induced IL2 responsiveness in the lymphocytes of the patients sensitized with OVA but not with Df; conversely, OVA-induced IL2 responsiveness was enhanced in Df- but not in OVA-sensitized lymphocytes. The CD45RA antibody apparently acts on CD4+ T cells, but not on CD8+ T cells, to induce the IL2 response. A further dissection of normal CD4+ T cells indicated that CD4+45RA- T cells preferentially respond to IL2 after stimulation with OVA or Df antigens. Since normal CD4+45RA+ T cells did not show antigen-induced IL2 responsiveness even after pretreatment with the CD45RA antibody, it is unlikely that the CD45RA antibody stimulates CD4+45RA+ T cells to become responsive to IL2 after antigenic challenge. Alternatively, CD4+45RA+ T cells may modulate the activity of CD4+45RA- T cells, which are potentially responsive to IL2 by antigenic stimulation and thus provide tolerance in nonallergic lymphocytes. Collectively, a defective suppressor activity of CD4+45RA+ T cells may exist in patients with hen-egg allergy and/or bronchial asthma, which may cause lymphocytes to be hyperreactive to OVA or Df antigens.

Isoforms of the CD45 common leukocyte antigen family: markers for human T-cell differentiation

The diverse host defense and immunoregulatory functions of human T cells are performed by phenotypically heterogeneous subpopulations. Among the membrane antigens that are differentially expressed by reciprocal human T-cell subsets are the CD45RA and CD45RO isoforms of the common leukocyte antigen family, which have been hypothesized to identify "naive" and "memory" T cells, respectively. The CD45RA antigen is first expressed by T-lineage cells relatively late during their intrathymic maturation and continues to be expressed by most T cells in the immunologically naive neonate. With increasing age and antigenic exposure, however, CD45RA-/RO+ cells become more prevalent in the circulation and comprise the majority of cells in tissues. Analyses of the functional capabilities of CD4+CD45RA+ and CD4+CD45RO+ cells have shown that proliferative responses to "memory" recall antigens or the ability to provide help for antibody production are functions uniquely performed by CD4+CD45RA-/RO+ cells. The major immunoregulatory functions described for CD4+CD45RA+ cells involve suppression of immune responses, either directly or via the induction of suppressor activity by CD8+ cells. Two general models of differentiation have been proposed to describe the lineal relationship of these T-cell subsets. Although these subsets could represent mature, phenotypically and functionally stable progeny arising from separate differentiation pathways, there is considerable experimental support for the hypothesis that CD45RA-/RO+ cells are "memory" cells that derive from "naive" or "virgin" CD45RA+/RO- precursors via an activation-dependent postthymic differentiation pathway. Altered frequencies of CD45RA+ and CD45RO+ T cells have been observed in a variety of different clinical conditions, particularly diseases manifesting altered immune function. These findings have contributed new information concerning the physiological events regulating the in vivo generation of these T-cell subsets. In addition, they may provide clues to the pathogenetic processes associated with certain diseases.

Impairment of helper T-cell function following severe head injury

Major infections, such as sepsis and pneumonia, occur in 50-75% of patients following isolated severe head injury. Previous studies have demonstrated that this high incidence of infection following severe head injury may be related to a decrease in helper T-cell activation and function. The present study was designed to investigate the effect of severe head injury on specific subgroups of helper T cells known to enhance or suppress cellular immune function. Specifically, peripheral blood lymphocytes (PBLs) from 10 head-injured patients and 10 matched controls were evaluated following in vitro stimulation with the T-cell mitogen, phytohemagglutinin (PHA). Subsets of helper T cells evaluated included activated helper (CD4+/CD25+) T cells; helper/inducer (CD4+/CDw29+) T cells, which enhance cellular immune activity; and suppressor/inducer (CD4+/CD45R+) T-cells, which induce suppressor (CD8+) T-cells. In addition, the effect of intraventricular fluid (IVF) on PHA-stimulated in vitro CD4 and CD25 expression was investigated to determine whether severe head injury results in the production of mediators within the central nervous system capable of affecting T-cell activation. The results of this study indicate that isolated severe head injury selectively reduces the ability of PHA-stimulated PBLs to express the helper/inducer (CD4+/CDw29+) T-cell (p = 0.023) and activated helper (CD4+/CD25+) T-cell (P = 0.041) phenotypes. There was no significant change in PHA-stimulated CD4 or CD25 expression following incubation of PBLs with intraventricular fluid (IVF) from head-injured patients. The relationship between these changes in specific helper T-cell subpopulations and the infectious complications of severe head injury are discussed.

Impaired autologous mixed-lymphocyte reaction of peripheral blood lymphocytes in adult periodontitis

The autologous mixed-lymphocyte reactions (AMLR) of peripheral blood lymphocytes from 80 patients with adult periodontitis were examined. Some but not all patients showed clearly low AMLR responses; 31 of 80 subjects (39%) showing consistently low responses in AMLR (less than the mean--2 standard deviations of the healthy control group values) were designated low-AMLR patients, whereas the 42 patients (53%) who showed normal AMLR responses were designated normal-AMLR patients. However, there were no significant differences in the clinical parameters between these two groups of patients. The phenotypic analysis of T-cell fractions revealed a lower percentage of CD45RA-positive cells in CD4-positive cells (CD4+ CD45RA+ T cells) in the low-AMLR patients than those in normal-AMLR patients and healthy control subjects. No significant differences were demonstrated between the two groups in terms of the proportion of CD4-positive and CD8-positive cells in the T-cell fractions or in the expression of human leukocyte antigen DR of the monocytes and B cells in the non-T-cell fractions. In the low-AMLR patients, the allogeneic MLR was found to be normal, but the interleukin 2 production in the AMLR was found to be significantly depressed. The depressed AMLR responses and the lower percentage of CD4+ CD45RA+ T cells in the low-AMLR patients were found to be normalized following the periodontal therapy. These results might reflect changes in regulatory T-cell function induced by development of periodontal diseases.

CD45 isoforms associated with distinct functions of CD4 cells derived from unusual healthy donors lacking CD45RA- T lymphocytes

We now report two healthy individuals whose T lymphocytes were over 95% positive for CD45RA antigen expression. However, these donors normally expressed both the CD29 high (CD29+) and CD45RO high (CD45RO+) antigens on approximately 40 and 50% of their CD4 cells, respectively. Despite the strong CD45RA expression on the surface of almost all CD4 cells, the CD29 marker allowed T cells from these donors to be divided phenotypically into subsets having distinct in vitro function. CD4+CD29+ cells from these donors responded maximally to recall antigens such as TT and provided strong helper function for B cell Ig synthesis. In contrast, CD4+CD29- cells responded poorly to recall antigens and had poor helper function for B cell Ig synthesis, but had strong suppressor activity. Thus, CD29 antigen expression was still predictive of the in vitro functional activity as previously described for normal donors. Furthermore, biochemical analysis of the distribution of individual CD45 isoforms on the surface of these subsets of CD4 cells revealed distinct differences. The CD4+CD29 high (CD4+CD29+) subset of cells primarily expressed the 180-, 190-, and 205-kDa CD45 isoforms, while the CD4+CD29 low (CD4+CD29-) cells primarily expressed the 190-, 205-, and 220-kDa CD45 isoforms. These results suggest that despite the superficial phenotypic similarity of CD4 cells in these donors, distinctions in the distribution of both CD29 and the 180- and 220-kDa CD45 isoforms exist and might play a role in the different functions of freshly isolated CD4 lymphocytes.

The role of CD45RA on human B-cell function: anti-CD45RA antibody (anti-2H4) inhibits the activation of resting B cells and antibody production of activated B cells independently in humans

Anti-CD45RA antibody defined by anti-2H4 monoclonal antibody has been reported to split CD4+T cells into two distinct subpopulations. CD45RA antigen is present on the surface of virtually more than 95% B lymphocytes in the purified tonsillar B-cell preparations. We examined the role of CD45RA antigen on human B-cell function using this antibody. The addition to anti-2H4 to tonsillar B cells inhibited the proliferative response induced by Staphylococcus aureus Cowan strain I(SAC) in a dose-dependent manner. Kinetic analysis indicated that anti-2H4 exerted its inhibitory effect when added within the first 24 h of culture initiation during a 72-h culture period. Anti-2H4 inhibited the transferrin receptor expression without interfering with the expression of the IL-2 receptor on SAC-stimulated B cells in a short-term culture. Anti-2H4 blocked the progress of SAC-stimulated B cells from the G1 to S phase of the cell cycle. These events suggested that anti-CD45RA MoAb inhibited the proliferative response by directly acting on B cells in the G1 phase. In addition, anti-CD45RA antibody also had a suppressive effect on early phase of B-cell differentiation. This effect appeared to be independent of its suppressive effect on proliferation, because anti-CD45RA did not inhibit the proliferative response of preactivated B cells with lymphokines. These studies suggested that the restricted epitope recognized by anti-2H4 antibody may be directly involved in regulatory function on B cells.

T cell interactions in active rheumatoid arthritis: insights from the human autologous mixed lymphocyte reaction as a model of T cell activation cascade

The autologous mixed lymphocyte reaction (AMLR) represents the activation, proliferation and differentiation of T cells in response to signals from autologous non-T cells. Using monoclonal anti-Leu8 antibody to isolate subpopulations of human CD4+ and CD8+ T cells, we have investigated the role of these subpopulations in the T cell activation cascade during the course of AMLR. In normal subjects, CD4+Leu8+ cells are necessary for the initiation of the AMLR response, and sequentially lead to activation and proliferation of both CD4+Leu8- cells and CD8+Leu8+ cells. The activated CD8+Leu8+ cells, in turn, induce CD8+Leu8- cells to generate proliferation of the latter cells. Soluble mediators could be involved in the T cell activation cascade induced by the AMLR. Patients with active rheumatoid arthritis have a profound defect in the AMLR. Further analysis indicates that rheumatoid arthritis CD8+ T cells are markedly defective as responding cells in the AMLR. The impaired AMLR response by CD8+ cells cannot be reconstituted with AMLR-derived supernatants from normal T cells. The data suggest that the defective CD8+ T cell function may contribute to the pathogenesis of the disease.

Immune system-associated antigens on the surface of peripheral blood lymphocytes in patients with Alzheimer's disease

We investigated the immune-associated antigens of peripheral lymphocytes from 13 patients with Alzheimer's disease (AD) and 13 age-matched healthy control subjects using two-color analysis with flow cytometry. Four ratios of immune-related antigens, T/B lymphocytes, CD4/CD8, CD4/CD45R and CD4/HLA-DR, were compared for the AD and control groups. The T/B and CD4/CD8 ratios did not differ between the groups, the ratio of CD4+CD45R+ subset in the AD group was lower than the ratio in the control group, and the ratios of CD4+ CD45R- and CD4+HLA-DR+ subsets in the AD group were significantly higher. Further, in the AD group, the CD4+ CD45R+/CD4+ ratio was lower and the CD4+ CD45R- CD4+ ratio was higher than in the control group.

Con A-induced suppressor cell function depends on the activation of the CD4+CD45RA inducer T cell subpopulation

Human T cells incubated for 48 hr with Con A suppress B cell Ig production. We sought to define the interactions between CD4+ T cells and CD8+ T cells in the generation of suppressor cell activity following Con A stimulation. Con A-activated CD4+ inducer T cells suppressed Ig production in autologous cocultures of T cells and B cells by 84%, while PHA-activated CD4+ T cells could not. However, Con A-activated CD4+ T cells are not themselves suppressors. When Con A-activated CD4+ T cells were added to coculture of B cells plus T cells depleted of CD8+ T cells, no suppression of Ig production was observed. Furthermore, these Con A-activated CD4+ T cells were able to provide excellent help for Ig production. Therefore, Con A-induced suppressor cell function requires a CD4+ suppressor/inducer acting on a CD8+ suppressor/effector ultimately resulting in the down regulation of B cell Ig synthesis. Human CD4+ inducer T cells can be functionally dissected into helper/inducer or suppressor/inducer T lymphocytes based on their expression of either the CDw29 or CD45RA surface molecules, respectively. Following incubation with Con A the expression of CD45RA on CD4+ T cells increased from 34 to 80% (P = 0.001) while CDw29 expression was unchanged. Incubating lymphocytes with PHA resulted in a non-specific increase in both CD45RA and CDw29 expression by CD4+ T cells. The increase in CD4+CD45RA expression was a result of active proliferation by the Con A-stimulated T cells. Suppression of Ig secretion was directly correlated with the enhanced CD45RA expression following Con A activation. We demonstrate that enhanced suppressor/inducer function is unique to Con A stimulation and was not observed following activation by PHA. Furthermore, short-term culture with Con A results in the selective expansion of the CD4+CD45RA T cell subpopulation.

T8 cell regulation of human B cell responsiveness: regulatory influences of CD45RA+ and CD45RA- T8 cell subsets

The immunoregulatory functions of human T8 cell subpopulations defined by mAb to the CD45RA molecule (2H4) were examined. Both CD45RA+ and CD45RA- T8 cells that had been treated with mitomycin C provided help for the production of immunoglobulins by B cells in cultures stimulated with immobilized mAb to CD3 (64.1). In contrast, both CD45RA+ and CD45RA- T8 cells that had not been treated with mitomycin C suppressed B cell responses in anti-CD3-stimulated cultures, although CD45RA+ T8 cells were more effective in this regard. Interleukin 2 (IL2) enhanced suppression by anti-CD3-activated CD45RA- T8 cells, whereas suppression by CD45RA+ T8 cells was almost maximal and not as much increased by IL2. The differentiation into suppressor-effector cells in this system appeared to involve the production of IL2, but not the production of interferon (INF)-gamma. Thus, CD45RA+ T8 cells produced higher amounts of IL2 but lower amounts of IFN-gamma than CD45RA- T8 cells in anti-CD3-stimulated cultures. Moreover, addition of mAb to the p55 component of IL2 receptor (anti-Tac) inhibited the generation of suppressor activity from CD45RA+ and CD45RA- T8 cells. The pattern and magnitude of suppression of B cell responses by CD45RA+ and CD45RA- T4 cells were similar to that by CD45RA+ and CD45RA- T8 cells in this system. Finally, preactivated CD45RA+ T8 cells that had lost CD45RA expression suppressed the B cell responses as effectively as fresh CD45RA+ T8 cells. The results indicate that both CD45RA+ and CD45RA- T8 cells can help or suppress B cell responses. More importantly, the data suggest that the suppressor-effector function of human T cells may rather be related with the stages of the post-thymic differentiation as evidenced by the expression of the CD45RA molecule than represent the fully differentiated T cell subsets, such as T4 and T8 cells. In addition, the CD45RA molecule appeared not to be involved in the suppressor-effector function, but to determine the stage of post-thymic differentiation.

Interleukin-1 corrects the defective autologous mixed lymphocyte response in multiple sclerosis

Patients with chronic progressive multiple sclerosis (MS) have alterations of T cell regulation that can be measured by in vitro assays and include decreases of the autologous mixed lymphocyte reaction (AMLR). Whether a defect in cytokine secretion was involved in the altered AMLR was investigated in 29 MS patients and 13 age- and sex-matched controls. The response of CD4+ T cell populations to irradiated non-T cells was decreased in MS as compared to control subjects. As previously reported, decreases in the AMLR were similarly observed with whole T cells of MS subjects as compared to controls. The addition of recombinant interleukin (IL)-1 to cultures of either whole T cells or CD4+ T cells with irradiated non-T cells in the AMLR corrected the immune defect in subjects with MS but had no effect on the AMLR in control subjects. In contrast, addition of rIL-2 or rIL-4 to the AMLR did not correct the decreased AMLR in MS patients as compared to controls. The lymphokines IFN-gamma and TGF-beta 2 both decreased the AMLR in MS patients and controls while TNF had no effect. Further, the magnitude of the AMLR response corresponded to IL-1 secretion induced by LPS in the non-T cell population. These studies indicate that defects in IL-1 may be related to immune defects of suppression in MS patients. Selective correction of immunoregulatory defects using lymphokines or their inducers in subjects with autoimmune diseases such as MS may be possible.

Age-related changes in the activation requirements of human CD4+ T-cell subsets

In agreement with previous studies, we found that the proliferative response of unfractionated T-cells to phytohaemagglutinin (PHA) was severely impaired in healthy aged individuals (70-85 years). On the other hand, we did not observe significant differences between aged and young adults in T-cell responsiveness to mab OKT3 (anti-CD3). PHA responses in "old" T-cells could be substantially improved, however, by the addition of recombinant interleukin-2 (rIL-2) or KOLT2 (anti-CD28 mab). When individual CD4+ T-cell subpopulations were isolated from young and old donors and stimulated with PHA in the presence of autologous accessory cells, age-related deficiencies were seen in both CD4+CD45RA+ (naive) and CD4+CD45RO+ (memory) cell populations. Further analysis using a panel of coactivators in cultures depleted of accessory cells identified specific abnormalities in the CD2 or alternate pathway of T-cell activation. These were predominantly seen in CD4+ naive T-cells. The capacity of rIL-2, KOLT2, and PMA to restore, at least partially, T-cell responsiveness in the aged suggests a defect(s) in an early signal transduction mechanism.

Identification of a cord blood T cell subset of CD3+4-8-45R+ suppressing interleukin 2 production in the autologous mixed lymphocyte reaction and the mode of action of exogenous IL2 in the induction of IL2 production

As previously reported, the inability of cord blood T cells to produce IL2 in the autologous mixed lymphocyte reaction (AMLR) could be recovered by the treatment of stimulator non-T cells with interferon-gamma (IFN-gamma) and of the AMLR with exogenous IL2. In the present study, we showed that addition of untreated autologous cord blood T cells to the above-mentioned AMLR abrogated the IL2 production in a dose-dependent manner, suggesting active suppression by the untreated T cells because untreated cord blood T cells did not consume IL2. Suppressor activity was abrogated by the treatment of cord blood T cells with monoclonal anti-CD3 antibody plus complement or with monoclonal anti-CD45R (Leu 18) antibody, but not by the treatment with monoclonal anti-CD4 antibody and/or anti-CD8 antibody plus complement. These data showed that the cord blood suppressor T cells were CD3+4-8-45R+. This suppressor activity also disappeared by culturing with rIL2 for 8 hr. As the frequency of CD45R+ cord blood T cells was comparable to that of CD45R+ adult T cells and was minimally affected by the IL2 treatment, functional modulation of CD45R+ suppressor T cells by IL2 is suggested. Moreover, in spite of the inhibitory effect of anti-CD45R antibody on the suppressor activity, IL2 production was not induced merely by addition of anti-CD45R antibody directly to the responder cells in AMLR. Taken together, these data suggest the requirement of exogenous IL2 for IL2 production in that IL2-producing-precursor T cells themselves should be stimulated by IL2 in addition to the modulation of CD45R+ suppressor T cells by IL2.

CD4+CD45RA+ and CD4+CD45RA- T cell subsets in man maintain distinct function and CD45RA expression persists on a subpopulation of CD45RA+ cells after activation with Con A

We have previously shown that Con A-induced suppressor T cells belong to the CD45RA+ subset. After unseparated T cells are activated with Con A, CD45RA expression increases to a maximum (Day 2), and then decreases significantly, but does not disappear entirely (Day 9), while CD29 expression increases steadily. In the present study, we examined the fate of these cell surface molecules on isolated CD4+CD45RA+ and CD4+CD45RA- cells following activation with Con A, and their relationship to the regulatory functions of these subsets. After activation of CD4+CD45RA+ cells with Con A, CD45RO and CD29 antigen expression rapidly increases (greater than 90%). While CD45RA expression is downregulated, approximately 40% of the cells continue to express low-density CD45RA in a stable fashion through Day 21. Despite these phenotypic changes, cells originally CD45RA+ continue to suppress IgG synthesis and provide only minimal B cell help. Furthermore, when cells originally CD45RA+ were sorted on the basis of continued presence, or loss of CD45RA antigen 14 days after activation, both populations demonstrated potent suppression and minimal help. In contrast, after activation with Con A, CD4+CD45A- cells maintain stable phenotype and provide significant help and minimal suppression. Immunoprecipitation of the CD45RA antigen from Day 14 activated CD4+CD45RA+ cells confirms the continued presence of the 205-kDa isoform, but reveals a significant decrease in the 220-kDa isoform. These results suggest that after activation with Con A, cells originally CD45RA+ remain functionally distinct from cells originally CD45RA-, and that CD45RA antigen persists on a subpopulation of CD45RA+ cells after activation with Con A.

Autologous mixed lymphocyte reaction is reduced in patients with psoriasis

The autologous mixed lymphocyte reaction (auto-MLR) was studied to test the interactions between immunocompetent cells in patients with psoriasis. The auto-MLR in 20 patients with psoriasis was significantly lower than in 16 normal controls. Lower values were found in untreated psoriatic patients than in those in remission following treatment. The values in the latter group were significantly lower than in controls and in six patients with atopic dermatitis in remission. The tendency for an increase in the auto-MLR with a decrease in disease activity was further confirmed in five patients studied before and after treatment. In contrast, the allogeneic lymphocyte reaction (allo-MLR) in psoriatics was similar to that in normal controls.

In vivo regulation of the murine syngeneic mixed lymphocyte reaction

Previous work from this laboratory has suggested that a CD8+ T suppressor (Ts) cell network regulated the murine syngeneic mixed lymphocyte reaction (SMLR). We have attempted to disrupt this network by the inoculation of anti-CD8 monoclonal antibodies (mAb) in vivo. Intraperitoneal inoculation of three mAbs resulted in a marked increase in the proliferation of CD4+, self-Ia-reactive splenic T cells in vitro to syngeneic, but not to allogeneic, spleen cells. Suppression was not limited to a specific mouse strain as the enhanced SMLR was reproducible following anti-CD8 treatment of three strains of mice. In vivo depletion of CD8+ T cells was not a prerequisite for enhancement of the SMLR as several mAb to CD8 augmented the SMLR independent of their capacity to cause CD8 T cell depletion. Moreover, enhancement of the SMLR could be mimicked in vitro by inclusion of anti-CD8 mAb in in vitro cultures of responder T cells and irradiated Ia+ syngeneic stimulators. Since the in vitro SMLR was enhanced following mAb treatment, it was expected that the in vivo SMLR would also be increased. However, no evidence of increased in vivo autoreactivity could be detected following in vivo treatment with anti-CD8 mAb, indicating that other mechanisms in addition to CD8+ regulatory T cells acted to regulate the in vivo activity of autoreactive T cells.

Effect of activation of protein kinase C on CD45 isoform expression and CD45 protein tyrosine phosphatase activity in T cells

The T200/leukocyte common antigen (CD45) is a family of at least five large-molecular weight glycoproteins, which are differentially expressed on T cell subsets. The CD45 antigen consists of a variable heavily glycosylated exterior domain, a single membrane-spanning region, and a large cytoplasmic domain that has protein tyrosine phosphatase (PTPase) activity. In this study, we examined the effects of activation of protein kinase C (PKC) on the phosphorylation and expression of CD45 isoforms and PTPase activity in human T cells. After activation of PKC by phorbol 12-myristate 13-acetate (PMA), CD45RA expression rapidly increased within the first 24 h, whereas CD45R0 expression did not change within this time. However by 48 h, expression of CD45R0 also began to increase. Metabolic labeling showed that the rapid increment in CD45RA expression observed after PMA stimulation is primarily due to increased de novo synthesis of the 205-kDa and not the 220-kDa molecule. PMA treatment resulted in the phosphorylation of each CD45 isoform to a degree corresponding to its relative surface expression. Significantly, we found that the phosphorylation of CD45 by PKC activation down-regulated CD45 PTPase activity.

Relationship between the synthesis of autoimmune antibodies and the formation of clusters of B, T and APC cells during the syngeneic mixed lymphocyte reaction in BALB/c and NZB mice: a technique for isolation of the spleen autoimmune compartment of non-immunized pathogen-free mice

Cells from the spleens of non-immunized mice were cultured in horizontal tubes, rotating very slowly around their long axis. Under these conditions, the flux speed gradient of the cell suspension near the tube walls greatly increased the chances of cells coming into contact with one another. Mixed clusters of B, T and APC cells were soon found adhering firmly to the walls of the tube; cluster formation leveled off after about 3 h. The clustered cells were easily separated from those remaining in suspension and constituted a particular cell compartment comprising a maximum of 20-30% of the total. B cells from this compartment, cultured in complete medium for 48 h, almost exclusively produced IgM antibodies. Antibodies reacting with self antigens were so numerous in the culture medium that it is likely all IgM were self antibodies. That the clusters obtained under these conditions constituted a compartment of autoimmune cells is supported by previous work which showed that 20-30% of spleen cells secrete IgM antibodies almost exclusively. Cluster formation as a function of age was compared in NZB mice which are used as a model of lupus erythematosus, and in BALB/c mice which never manifest self-immune pathology. The number of cells found in clusters per whole spleen increased exponentially with age in NZB mice and linearly in BALB/c mice. The production of autoimmune antibodies as a function of age also increased exponentially for NZB mice and linearly in BALB/c mice, which provides further striking support for the hypothesis that the clusters formed constitute the autoimmune comportment.

CD4+ cells treated with DNA methylation inhibitors induce autologous B cell differentiation

The DNA methylation inhibitor 5-azacytidine induces autoreactivity in cloned CD4+ T cells, but the functional consequences of this response are unknown. We now report that CD4+ T cells treated with 5-azacytidine respond to autologous antigen-presenting cells and induce autologous B cell differentiation without exogenous antigen or mitogen. This mechanism could play a role in some autoimmune diseases characterized by T cell DNA hypomethylation and polyclonal B cell activation.

The functional heterogeneity of CD8+ cells defined by anti-CD45RA (2H4) and anti-CD29 (4B4) antibodies

The monoclonal antibodies, anti-2H4(CD45RA), and anti-4B4(CD29), along with UCHL1-(CD45RO), identify reciprocal populations of CD4 cells with distinct suppressor inducer (CD45RA+CD29-CD45RO-) and helper inducer (CD45RA-CD29+CD45RO+) functions. Although the CD8+ population is known to contain precytotoxic, cytotoxic, suppressor, and some natural killer cells, the exact phenotypic identities of these functional CD8 subsets has not been established. In this study, we tried to determine whether these monoclonal antibodies could distinguish functionally distinct subsets of cells within the CD8+ population. For this purpose, whole T cells or fractionated T cells were sensitized with irradiated allogeneic non-T cells for 6 days, following which, CD8+ or CD8+CD11b- cells were isolated and cellular functions such as suppressor, killer precursor, and killer effector activity were assessed. The results showed that both class I-restricted alloantigen-specific killer effector and killer precursor cells belonged to the CD8+CD11b-CD45RA-CD29+ population. Moreover, these killer effector cells expressed the CTL-associated S6F1 molecule, an epitope of the LFA-1 antigen. In contrast, suppressor effector cells belonged to the CD8+CD11b-CD45RA+CD29- cell population. Although the UCHL1 antigen has been reported to define the CD4+CD29+ helper inducer cell, over 90% of allo-activated CD8+ cells expressed this antigen, whereas only 40-60% of these cells expressed either CD45RA or CD29 antigens. These results suggest that anti-CD45RA and anti-CD29 antibodies may provide useful tools for distinguishing between suppressor effector versus killer effector and killer precursor cells within the CD8+CD11b- population.