Spleen lymphocyte populations and expression of activation markers in rats treated with the potent new immunosuppressive agent FK-506

Rats were immunized systemically with sheep red blood cells (SRBC) and treated with either FK-506 (1 mg/kg/day) or cyclosporin A (CsA) (25 mg/kg/day) for 7 days. Profound (greater than 90%) suppression of the production of splenic IgM-secreting plasma cells and circulating antibody levels was observed in animals receiving either drug. Immunosuppression was accompanied by significant increases in the incidence and absolute numbers of OX8+ (T-cytotoxic/suppressor) lymphocytes in the spleen, and there were corresponding reductions in the W3/25+:OX8 (CD4+:CD8+) ratio. The magnitude of these changes was not affected by drug combination. There were no significant alterations in B cells with either agent, whilst a small but significant increase in the incidence of macrophages was observed in all drug-treated groups. Neither FK-506 nor CsA affected IL-2 receptor (OX39) or MHC class II (OX6) antigen expression. This study demonstrates the remarkable immunosuppressive potency of FK-506 and its underlying capacity, like CsA, to affect regulatory T-lymphocyte subsets in vivo.     

Immunosuppressive drugs have different effect on B lymphocyte subsets and IgM antibody production in immunized BALB/c mice

Infections are frequently associated with immunosuppressive therapy currently used to prevent organ rejection or treat autoimmune diseases. Such drugs suppress antibody production despite having different mechanisms of action. Antibodies are produced by a non-homogenous population of B lymphocyte subsets. B-1 cells produce natural antibodies and protect immediately after infection, while B2 cells produce antigen-specific IgM antibodies in a later response to infection. To understand how the immunosuppressive drugs affect antibody production by B cell populations, we immunized BALB/c mice with different antigens followed by administration of various immunosuppressive drugs. B-1a and B-1b lymphocytes from spleens of sacrificed animals were analyzed by flow cytometry, natural and antigen –specific IgG and IgM antibodies were determined by nephelometry and ELISA assays. Results showed that prednisone (PDN), cyclophosphamide (CYC), methotrexate (MTX), mycophenolate mofetil (MMF) and azathioprine (AZA) decreased more than 60% of B-1a lymphocytes while cyclosporine (CsA) had little effect. Three drugs PDN, AZA and CYC suppressed the B-2 cells on day 30, while MTX affected this subpopulation early on day 5. Antigen-specific IgM antibodies were dramatically suppressed after 15 days of immunization in animals receiving PDN, CYC or AZA, while MMF, CsA and MTX showed little effect. Natural antibodies were equally decreased in all animals regardless of the specific drug used in treatment. These results will help to choose single or combinations of immunosuppressive drugs in the clinical setting.     

Early induction of MHC antigens in human liver grafts. An immunohistologic study.

The present study documents major histocompatibility complex (MHC) Class I and II expression during early acute rejection of human liver grafts. Serial graft biopsies (pretransplant, time zero, and 1 week) were studied. Ten patients received azathioprine (AZA) and prednisone; the other six patients were treated with quadruple therapy (azathioprine, cyclosporine A, prednisone, and cyclophosphamide). To study the specificity of changes in MHC antigen expression, biopsies of six patients with minor or no morphologic abnormalities served as controls. In addition, phenotypes of inflammatory cells present during rejection were analyzed using a panel of monoclonal antibodies. The results show that during acute rejection expression of MHC Class I and II antigens increased significantly in the AZA-treated patients, in a pattern similar to that seen in the patients treated with quadruple therapy, showing enhanced MHC Class I expression on hepatocytes, bile duct epithelium, and sinusoidal endothelium, and Class II antigen on Kupffer cells and sinusoidal endothelium. Bile duct epithelium was consistently positive for Class II antigen; no significant difference with the nonrejection group was observed. T cells are the predominant inflammatory cells during rejection with equal quantities of CD4+ and CD8+ cells. A majority of the infiltrating T cells show expression of Class II antigen but do not react with anti-interleukin-2 receptor antibody. This may be the result of immunosuppressive therapy or a simple reflection of the temporary expression of interleukin-2 receptors during lymphocyte activation. The authors hypothesize that the induction of MHC antigens on bile duct epithelium leads to rejection whereas the expression on hepatocytes represents an epiphenomenon.     

Monoclonal antibody analysis of Listeria monocytogenes-induced cytotoxic lymphocytes.

An immunizing infection with Listeria monocytogenes provides a potent stimulus for the formation of prekiller lymphocytes. Their cytolytic potential is revealed when the cells are restimulated in vitro by Listeria antigens. Listeria monocytogenes-induced cytotoxic lymphocytes and the prekiller cells from which they are derived were characterized in respect to their surface antigenic markers. Using monoclonal antibodies, B-cell depleted lymphocytes from the thoracic duct of Listeria immune rats were fractionated into subsets by a combination of panning and sorting techniques. Listeria monocytogenes-induced cytotoxic lymphocytes and their prekiller cell precursors were demonstrated to have the phenotype W3/25-, OX8+, OX4+, W3/13+ (high density), OX19+ (low density), RT6.1-. The OX8+, RT6.1- subset, which contained prekiller cells, constituted approximately 6% of lymph-borne T cells. The data indicate that these microbial antigen-induced cytotoxic lymphocytes belong to a minor subset of peripheral T cells whose surface antigenic properties distinguish them from natural killer cells.     

The effect of 2-acetyl-4-tetrahydroxybutylimidazole on lymphocyte subsets in peripheral blood of the rat

A constituent of Ammonia Caramel, 2-acetyl-4-tetrahydroxybutylimidazole (THI), is known to cause a reduction in the number of circulating lymphocytes when fed to rats. In the present study the effect of giving THI 1 mg/kg by gavage daily for 7 days on the numbers of lymphocytes in subsets has been monitored in peripheral blood. Both immunoglobulin light chain-bearing B-cells (MARK-1+) and CD5 marker-bearing T-cells (OX-19+) were reduced in number within 1 day of treatment. Within the pan-T-cell population, Class II MHC reactive helper T-lymphocytes (W3/25-) were more reduced than the Class I MHC reactive cytotoxic/suppressor T cells (OX-8+). The number of null cells (MARK-1-, OX-19-) was not affected; the majority of these cells appeared to be large granular lymphocytes.     

Two subsets of rat T lymphocytes defined with monoclonal antibodies

A new monoclonal mouse antibody that recognizes a subset of rat peripheral T cells has been prepared by immunizing mice with rat thymocyte glycoprotein. This antibody, designated MRC OX 8, labels all peripheral T cells that are unlabeled by the previously described W3/25 monoclonal antibody. No peripheral T cells were found that bound both antibodies, but, in contrast, 90% of thymocytes were doubly labeled. Thoracic duct lymphocytes of congenitally athymic nude rats were not labeled by either antibody, but the spleens of such animals contained both W3/25⁺ cells and MRC OX 8⁺ cells. These splenocyte subpopulations did not overlap. Using the fluorescence-activated cell sorter to isolate cells binding MRC OX 8 antibody, the phenotype of T cells mediating various T cell functions was established. Combining the present results with those published previously, it is shown that the cells providing help for antibody responses and those mediating graft-vs. -host reactions are phenotypically W3/25⁺ MRC OX 8^?. On the other hand, parental T cells that suppress antibody formation in F₁ hosts were identified as W3/25^? MRC OX 8⁺. The relationship between the rat T cell subsets defined by these antibodies and those in the mouse identified by the Ly series of alloantibodies is discussed and a comparison made between the rat W3/25⁺ subset and a recently identified human T cell subset.     

Allograft rejection in athymic nude rats by transferred T-cell subsets. I. The response of naive CD4+ and CD8+ thoracic duct lymphocytes to complete allogeneic incompatibilities

PVG.rnu/rnu nude rats were pre-grafted with two allogeneic skin grafts, AO(RTlu) and BN(RTln), 6-14 days in advance of cell transfer. Cellular requirements for rejection were established by transferring graded numbers of B cell-depleted (Ig-) thoracic duct lymphocytes (TDL) or purified W3/25+ (CD4+) or OX8+ (CD8+) TDL subsets. Allografts were rejected by 10(5) to 5 x 10(6) Ig- TDL in a dose-dependent fashion. A similar dose-response relationship was found by transferring 5 x 10(5) to 5 x 10(6) Ig- OX8- TDL (purified by depletion of B cells and OX8+ cells). Larger numbers of Ig- OX8- TDL (10-30 x 10(6)) did not significantly accelerate rejection. W3/25+ TDL alone (10(5)), highly purified by fluorescence-activated cell sorting (FACS), were sufficient to induce allograft rejection in this athymic nude rat model. In contrast, 10 times more FACS purified OX8+ TDL (10(6)) were unable to initiate skin graft rejection despite the complete class I and class II MHC incompatibilities. Furthermore, the addition of 10(6) OX8+ cells did not accelerate or retard the rejection induced by 10(5) W3/25+ cells alone. Pre-grafted nude recipients, irradiated (500 R) 2 hr before W3/25+ TDL injection, in order to eliminate putative nude T cells, rejected allografts on the same day as unirradiated controls. We conclude that when confronted with complete MHC disparities, CD4+ T cells are necessary and sufficient to induce skin allograft rejection whereas CD8+ T cells do not appear to contribute.     

T Lymphocytes Subsets in Experimental Iron Overload

Several abnormalities of the immune system have been reported in association with clinical and experimental iron overload. To dissect further such abnormalities, changes in lymphocyte subsets were evaluated in iron-loaded male Sprague-Dawley rats. The iron-loading protocol consisted of a total dose of iron-dextran (1.5 mg/Kg body weight) divided in daily intramuscular injections over twenty consecutive days. At days 0, 20, and 50 after initiation of iron injections lymphocyte subsets in blood, spleen and mesenteric lymph nodes were estimated by indirect immunofluorescence using monoclonal antibodies recognizing T cells (W3.13), the subset of helper T cells in (W3.25), and the subset of cytotoxic T cells (OX.8). By day 20, there was no change in the number of W3.25+ T cells in the blood of iron-loaded animals as compared to the controls, but the OX.8 + T cells were significantly elevated. At this time, the ratio W3.25 ⁺/OX.8⁺ cells was significantly decreased (0.5 in experimental rats vs 2.0 in controls). Similar results were obtained at day 50. In the spleen, there was a decrease in the proportion of W3.25 ⁺T cells and an increase in OX.8⁺ T cells at day 20. However, these values returned to normal by day 50. A negative correlation between W3.25 ⁺/OX.8⁺ ratio and serum ferritin was observed in blood and spleen during iron administration. These changes were associated with abnormalities in lymphocyte proliferative response. No changes in W3.25 ⁺/OX.8⁺ ratio were observed in mesenteric lymph nodes. These results demonstrate that iron overload alters the distribution of T lymphocytes in various compartments of the immune system.     

Immunomodulatory effects of cyclophosphamide and implementations for vaccine design

Drug repositioning refers to the utilization of a known compound in a novel indication underscoring a new mode of action that predicts innovative therapeutic options. Since 1959, alkylating agents, such as the lead compound cyclophosphamide (CTX), have always been conceived, at high dosages, as potent cytotoxic and lymphoablative drugs, indispensable for dose intensity and immunosuppressive regimen in the oncological and internal medicine armamentarium. However, more recent work highlighted the immunostimulatory and/or antiangiogenic effects of low dosing CTX (also called "metronomic CTX") opening up novel indications in the field of cancer immunotherapy. CTX markedly influences dendritic cell homeostasis and promotes IFN type I secretion, contributing to the induction of antitumor cytotoxic T lymphocytes and/or the proliferation of adoptively transferred T cells, to the polarization of CD4(+) T cells into TH1 and/or TH17 lymphocytes eventually affecting the Treg/Teffector ratio in favor of tumor regression. Moreover, CTX has intrinsic "pro-immunogenic" activities on tumor cells, inducing the hallmarks of immunogenic cell death on a variety of tumor types. Fifty years after its Food and Drug Administration approval, CTX remains a safe and affordable compound endowed with multifaceted properties and plethora of clinical indications. Here we review its immunomodulatory effects and advocate why low dosing CTX could be successfully combined to new-generation cancer vaccines.     

Surface phenotype of T cells producing growth of mucosal mast cells in normal rat bone marrow culture.

We have previously shown that lymphocytes from Nippostrongylus brasiliensis infected rats, when stimulated with antigen or concanavalin A (Con A) release factors which are comparable with murine IL-3. On addition of these factors to rat bone marrow cultures, mast cells with the morphological and biochemical properties of mucosal mast cells (MMC) proliferate and mature. Here, we use this system, along with monoclonal antibodies against rat T cells and the fluorescence-activated cell sorter (FACS), to isolate the subset of T cells responsible for the production of this MMC growth factor. Lymphocytes from N. brasiliensis infected rats were separated on the FACs into populations with and without the antigens defined by OX19, W3/25 and OX8 monoclonal antibodies; these antibodies label all T cells, T-helper cells and T-cytotoxic/suppressor cells, respectively. The resultant subsets were cultured in vitro with Con A. The supernatants were tested for the ability to induce MMC growth and differentiation in liquid cultures of normal rat bone marrow. The phenotype of the T cells producing this factor was established as being OX19+, W3/25+ and OX8-.     

Recirculation of lymphocyte subsets (CD5+, CD4+, CD8+, T19+ and B cells) through fetal lymph nodes

The experiments reported in this paper examine the cell-surface phenotype (CD5, CD4, CD8, T19, MHC class II and sIg) and cell output of lymphocyte subsets circulating through a subcutaneous lymph node in the sheep fetus, in an environment unaffected by foreign antigen and circulating immunoglobulins. CD4+ lymphocytes were the major T-cell subset in fetal lymph and were clearly enriched in lymph compared with blood, whereas T19+, CD8+ and B lymphocytes were not. It seems likely that in the fetus CD4+ lymphocytes are extracted from the blood at a faster rate than are other T-cell subsets and B cells. There was a much higher percentage of CD8+ and T null cells and a lower percentage of MHC class II+ and B cells circulating in the fetal lymph than in adult lymph, while the percentage of T19+ lymphocytes in fetal blood was twice that in the adult. Although the hourly cell output from an adult prescapular lymph node was far higher than that from a fetal lymph node, the circulation of lymphocytes through fetal lymph nodes was much greater per gram lymph node weight than that through adult lymph nodes. The wholesale recirculation in the fetus of all the major T-cell subsets found in the adult is paradoxical because it is not known what function they serve in the fetus in the absence of antigen and ongoing immune responses, although clearly they are not memory cells.     

Effect of Cyclosporin A on the in Situ Inflammatory Response of Human Renal Allograft Rejection

Twenty cadaveric kidney allograft recipients were prerandomized into two groups. Ten patients (control group) were treated postoperatively with azathioprine (AZA) plus methylprednisolone (MP); the other ten received cyclosporin A (CyA) as the only immunosuppressive agent. Both groups received MP during rejection. One patient was excluded from the CyA group because of an early postoperative cardiac infarction and death. All transplants were monitored by alternate-day fine-needle aspiration biopsy and transplant aspiration cytology. Some patients treated with CyA had a significant initial decrease in urine output, reaching control values approximately 1 week postoperatively. The mechanism behind this deteriorated renal function is not clear, but it seemed to have been caused by injuries to the kidney tubular component, since a distinct monocytic-lymphocytic inflammation and severe cytological changes resembling pronounced acute tubular necrosis were observed concomitantly in transplant aspiration cytology. The CyA-treated patients had normal levels of blood leucocytes, thrombocytes and lymphocytes but displayed a strong early blood eosinophilia that was absent in the control subjects. During the first 30 days after transplantation 15 in situ episodes of inflammation were recorded in the nine transplants treated with CyA, whereas only 6 episodes were found in the 10 transplants receiving AZA + MP (P<0.01). The first inflammatory episode in the CyA-treated transplants peaked between days 5 and 8 after transplantation and was followed by another distinct inflammatory episode between days 23 and 26. In the AZA- plus MP-treated transplants, only one inflammation episode was observed, with a peak on day 14 postoperatively. The inflammatory cell types most prominently present in the CyA-treated transplants were lymphocytes, B plasmablasts and monocytes. The early inflammatory episodes in the CyA-treated transplants may have been related to the fact that during the initial intramuscular administration, therapeutic CyA concentrations in patient serum were not achieved until the fourth postoperative day during peroral administration. The onset of transplant function had no impact on the in situ inflammatory response of rejection in the CyA-treated transplants or on the concentration of CyA in patient serum. This indicates that CyA may also be used in initially non functioning transplants. Confirming our earlier results, we were unable to demonstrate the major histocompatibility complex (MHC) antigens on the healthy grafts treated with AZA plus MP. However, in healthy allografts treated with CyA, both classes of MHC antigens were nearly invariably demonstrable on the graft endothelial cell surface. Approximately 60% allograft survivals were recorded in both groups at 6 months, and all patients with functioning grafts were able to work.     

Accumulation of CD8+ Cells after Immunization with Soluble Antigen

Rats were immunized with ovalbumin, either subcutaneously or by aerosol inhalation. The lymphocyte distribution in lymph nodes, peripheral blood, and spleen was investigated by flow cytometry after labelling with T pan (OX19 and W3/13), T helper lymphocytes (W3/25), T cytotoxic/suppressor lymphocytes (OX8), kappa light chain (MAR 18-5), or MHC class II (OX6) monoclonal antibodies. The influence of the neurotoxic agent capsaicin on the lymphocyte distribution was also analysed. Subcutaneous immunization resulted in an increased number of OX8+ cells in mesenteric lymph nodes, spleen, and peripheral blood but not in the draining lymph nodes, axillary, brachial, and mediastinal lymph nodes. The number of positive cells for the other cell markers used were not affected by immunization. The neuromodulatory effect of capsaicin had no effect on the lymphocyte distribution. The results showed that the type of immunization used, low amounts of antigen without adjuvant given during a prolonged period, selectively induced OX8+ cells. The patterns were unaffected by neuromodulation using capsaicin.     

Suppression of the local graft-vs.-host reaction in rats by treatment with a monoclonal antibody specific for the interleukin 2 receptor

Local graft-vs.-host reaction (GVHR) was induced in rats by injecting parental cells into young F1 recipients. As a consequence of antigenic stimulation in the course of developing GVHR in the responding lymph nodes, the number of interleukin 2-receptor (IL 2R)-bearing T cells increased from less than 1% up to 10% of the total population. The IL 2R-bearing cells were located mainly in the T cell areas of the reactive lymph nodes. As assessed by the determination of the GVHR indices, treatment of the recipients with anti-T-helper subset-specific mAb (W3/25) or with anti-IL 2R mAb (ART-18) inhibited the GVHR. In parallel, the number of IL 2R-bearing cells was reduced to the normal levels. W3/25 mAb treatment changed the helper/suppressor subset ratio and reduced the number of circulating lymphocytes in the peripheral blood. In contrast, ART-18 mAb treatment did not induce any detectable changes in the subset distribution and it did not affect the number of circulating lymphocytes. The results demonstrate the key role that the IL 2R-positive cells play in the proliferative phase of acute GVHR, and favor the use of anti-IL 2R mAb as selective immunosuppressive agents.     

Effect of cyclosporin A on T cell immunity. I. Dose-dependent suppression of different murine T helper cell pathways

Cyclosporin A (CsA) is used as a clinical immunosuppressive agent. Despite its immunosuppressive potential, some studies involving in vivo administration of cyclosporin have failed to verify the immunosuppressive activity of this agent. The present study investigates the effect of different concentrations of CsA added in vitro, or of different doses of CsA administered in vivo, on the ability of murine spleen cells to produce interleukin 2 and to generate cytotoxic T lymphocytes in vitro when stimulated with TNP-self or H-2 alloantigens. The results indicate that self Ia-restricted T helper (Th) cells are more sensitive to lower doses of CsA than Th cells that are allorestricted. Thus, doses of CsA were found (15-30 mg/kg) that inactivated self Ia-restricted Th function, but not other Th or effector function. This Th cell defect could be partially corrected in vitro by addition of Th cell factors to the sensitization cultures. A higher dose (75 mg/kg) of CsA inactivated all detectable T cell responses, and this defect was not corrected by addition of Th cell factors. T cell function returned to normal levels within two weeks of cessation of CsA at all three doses of CsA tested. The selective loss of L3T4 Th function at the lower doses of CsA was associated with a radiosensitive, Ly-2 suppressor T cell that was selective in its action on self Ia-restricted Th cell function. Loss of all T cell function at the higher dose of CsA was associated with a radioresistant non-T suppressor cell that inactivated all T cell function tested. These results are discussed with respect to the selective dose-dependent effects of CsA on Th subsets, on the activation of suppressor cells with similar selectivity, and the implications of these findings on the use of CsA to prevent rejection of tissue allografts.     

Expression of MHC Class II antigens by oesophageal epithelium in herpes simplex oesophagitis

An immunoperoxidase technique with monoclonal antibodies for the identification of lymphocyte subsets and MHC Class II antigens was applied to oesophageal biopsies from two patients with herpetic oesophagitis. Oesophageal epithelial cells were found to express the MHC Class II antigen. The inflammatory infiltrate of the lamina propria was composed of both B lymphocytes and T lymphocytes.     

Changes in immunological parameters after conversion from cyclosporine A to azathioprine in renal transplant recipients

Long term CsA therapy did not interfere with the basal levels of natural killer (NK) activity in stable cadaveric renal transplant recipients. However, 3 months after changing immunosuppressive therapy from CsA to AZA, NK activity was significantly decreased (36 +/- 25% vs 19 +/- 15%, P less than 0.01). Following in vitro exposure to IFN-gamma an increase in NK activity from 36 to 44% (P less than 0.05) could be induced during CsA therapy but this was no longer observed after conversion to AZA (19 to 22%, N.S.). A prominent decline in the number of NK cells expressing the surface receptor for the Fc portion of IgG was also found postconversion. The IFN-gamma production capacity after mitogen stimulation of unprimed lymphocytes was more depressed during CsA than during AZA therapy (median 25 vs 80 U/ml 10(6) cells, P less than 0.05), suggesting a reversible inhibition of CsA on lymphokine production. Despite the better IFN-gamma production capacity, both the activity, inducibility and number of NK cells were significantly lower under AZA therapy than under CsA therapy. These findings indicate that CsA exerts its immunosuppressive action without an important interference with NK activity. Monitoring mononuclear cells showed a decrease in absolute numbers of all phenotypically distinct cells studied after conversion. The prominent decrease in CD 8 cells resulted in an increase of CD 4/CD 8 ratio.     

Immunobiology and immunotherapeutic implication of syneneic/autologous graft-versus-host disease

Summary: Administration of the immunosuppressive drug cyclosporine (CsA) after syngeneic/autologous bone marrow transplantation (BMT) elicits an autoimmune syndrome with pathology virtually identical to graft-vs-host disease (GVHD). The induction of this syndrome, termed syngeneic/autologous GVHD, is a two-tiered process requiring both the active inhibition of thymic-dependent clonal deletion and the elimination of mature T cells that have an immunoregulatory effect. Eradication of the peripheral immunoregulatory compartment by the preparative regimen provides a permissive environment for the activation of the syngeneic/autologous GVHD effector T cells. Although the repertoire of autoreactive effector T lymphocytes is highly conserved, these T cells promiscuously recognize MHC class II determinants. This novel specificity of the autoreactive lymphocytes appears to he dependent on the peptide derived from the MHC class 11 invariant chain. Recent studies also suggest that these promiscuous autoreactive T cells can effectively target and eliminate MHC class Il-expressing tumor cells. Administration of cytokines that upregulate the target antigen or expand the effector population can potentiate the antitumor activity of syngeneic/autologous GVHD, Although the induction of syngeneic/autologous GVHD is an untoward effect of CsA immunosuppression, mobilization of these autoimmune mechanisms provides a promising immunotherapeutic approach for certain neoplastic diseases.     

Autoimmune-mediated vasculopathy.

The use of the immunosuppressive drug cyclosporine A (CsA) in solid organ transplantation can be associated with the development of vasculopathy as part of the complex immune response involved in chronic rejection, including autoimmune recognition. Although CsA can directly affect endothelial cells, this drug alters the T cell repertoire promoting autoimmune recognition. The present studies evaluated the ability of CsA-induced autoreactive T cells to mediate vascular lesions in syngeneic heart grafts. Graft vasculopathy developed in syngeneic heart grafts following either the primary induction of autoimmunity with CsA or the adoptive transfer of CsA-induced autoreactive T cells. Initially, an inflammatory response occurred in the medial wall of the small arterial vessels, accompanied by a perivascular lymphocytic infiltrate (including a lymphocytic infiltrate into the myocardium), followed by progression of vascular disease with endothelial cell proliferation. The development and progression of vascular disease correlated with the cytokine profile of the infiltrating lymphocytes with type 1 cytokines detected early and type 2 cytokines detected as the disease progressed. Initiation of this response correlated with upregulation of the target antigen recognized by the CsA-induced autoreactive T cells, the MHC class II-invariant chain peptide complex. This antigen complex, when upregulated on endothelial cells by interferon, allowed effective targeting by the autoreactive T lymphocytes. Strategies to inhibit the upregulation of MHC class II antigens by treatment of the recipients with chloroquine truncated the disease process. The results of these studies suggest that CsA-induced autoreactive mechanisms can contribute to the development of graft vasculopathy.     

Glucocorticoid inhibitory action on the response to PHA of residual circulatory lymphocytes in renal transplant patients following immunosuppressive therapy

The inhibitory effect of glucocorticoids on the in vitro response to phytohaemagglutinin of the residual circulating T lymphocytes in renal transplant patients during maintenance immunosuppressive therapy with glucocorticosteroids and azathioprine has been investigated. As in normal subjects, the steroid-induced inhibition of transplanted patients' lymphocyte response was inversely correlated with the mitogen concentration used. On the other hand, the response of the various lymphocyte preparations from transplanted patients appeared less inhibited by steroids than the corresponding preparations from normal subjects. The addition to the culture of the adherent cell product interleukin 1 was effective in removing to a similar extent the steroid inhibitory effect on lymphocytes from normal and transplanted subjects. Thus, the lesser inhibitory effect of glucocorticoids on transplanted patient lymphocytes could be explained by the higher percentages of monocytes present in all peripheral blood mononuclear cell preparations. These results suggest that during immunosuppressive therapy with glucocorticoids and azathioprine the residual circulating lymphocytes have a responsiveness to in vitro dexamethasone suppression similar to that of normal peripheral blood lymphocytes.