Heat-inactivated (45 degrees C/1 hr) lymphocytes selectively activate suppressor T cells in the mixed lymphocyte reaction (MLR), while no significant proliferation and cytotoxic T lymphocyte activation can be detected. It is not well understood why hyperthermic treatment abolishes the stimulatory capacity of lymphocytes since HLA-DR molecules remain detectable immediately following heat exposure. In order to further characterize the requirements for Ts activation we studied the effects of hyperthermic treatment on cellular protein and DNA synthesis and cell surface protein expression in proliferating T and B cells; interleukin (IL)-1, IL-2, and IL-3 release following allogeneic stimulation with heat treated cells (HMLR); and IL-2 receptor expression as an indicator of T cell activation in the HMLR. Hyperthermic treatment reduced cellular protein synthesis as estimated by 14C-leucine uptake to about 15%, and DNA synthesis (3H-thymidine incorporation) to about 5% of untreated control cells. In contrast to y-irradiated cells, viability of heated cells rapidly declined within the first 24 hr. Hyperthermic treatment doubled binding of mouse immunoglobulin paralleled by an increased expression of IL-2 and transferrin receptors, while expression of HLA-DR and 4F2 proteins appeared unchanged. Stimulation with heated cells triggered the release of IL-1- and an IL-3-like bioactivity but did not induce IL-2 synthesis and/or release, thus explaining the lack of proliferation in the HMLR. Addition of exogenous IL-2 but not IL-1 restored HMLR proliferation. A comparison of allostimulation with y-irradiated and heat-treated cells revealed that significantly fewer T cells were induced to express IL-2 receptors at day 3 (14% vs. 8%, P less than 0.001) and at day 6 (42% vs. 21%, P less than 0.05) with heat-inactivated stimulators. We conclude that metabolically compromised lymphocytes activate Ts and are sufficient to stimulate IL-1 and IL-3 synthesis but do not transmit an unknown signal required for the activation of IL-2 synthesis and IL-2 receptor expression on a yet-to-be-defined T cell subset.

DNA↗

PubMed1986

Natural killer cell response to interferons.

The availability of recombinant interferons has facilitated a comparison of the in vitro effects of interferon-alpha and -gamma upon human natural killer (NK) cells. In the absence of interferon high and low NK responders exist. Repeated testing of the same individuals revealed different but stable NK patterns to in vitro addition of interferon-alpha and -gamma Furthermore, the NK cell response patterns differed depending on whether the interferons were administered in combination or separately. These studies suggest new complexities that must be addressed in the planning and execution of clinical interferon trials. The pattern of responsiveness of human NK cells to interferon-alpha or -gamma or both is highly variable, but stable, within a given individual.

Cytotoxicity, Immunologic↗

PubMed1985

Interleukin-2 apparently upregulates its receptor and induces proliferation of various resting mononuclear leukocytes in the absence of antigen.

We demonstrate that exposure to highly purified recombinant interleukin 2 (rIL-2) in the absence of known antigenic stimulation induces/increases the expression of two activation-associated proteins, the interleukin 2 receptor (IL-2R) and 4F2 on "resting" peripheral blood mononuclear cells (PBMC); subsequently, these cells enter the S phase of the cell cycle and proliferate. Dual parameter flow cytometry indicates that the phenotype of the cell population(s) which proliferate following this treatment includes HNK+, DR+, and T3+ cells. A twofold expansion in the number of HNK+ and DR+ cells was observed upon culturing resting PBMC in rIL-2 over a 6-day culture period. While the HNK monoclonal antibody is not specific for NK cells, these data do suggest that antigen independent growth of HNK+ cells may represent an additional mechanism by which IL-2 enhances NK effector activity, i.e., by induction of clonal growth of NK cells. In contrast, several concentrations of recombinant Interferon-gamma failed to produce a similar proliferative response.

Cell Separation↗

PubMed1985

Behavior of helper T lymphocytes in cyclosporine-mediated long-term graft acceptance in the rat.

(LEW X BN)F1 cardiac allografts are rejected acutely (7 days) in unmodified LEW rats, yet survive indefinitely following cyclosporine (CsA) treatment (15 mg/kg im for 7 days) or in T-cell-deprived (B) recipients. Using these models, the function of T helper cells (Th) in the maintenance phase of CsA-mediated long-term graft survival was examined. With monoclonal antibody immunoaffinity fractionation techniques, Th (W3/25+OX8-) were separated from spleens of CsA-treated hosts 3-4 weeks after grafting (CsA-Th), from specifically sensitized (s-Th), or from normal ungrafted (n-Th) rats. Adoptive transfer of 60 X 10(6) CsA-Th into B recipients produced rejection of donor-specific, but not third-party grafts in 21 +/- 7 days, comparable to s-Th (17 +/- 4 days), but faster than n-Th (4-5 weeks, P less than 0.025). CsA-Th recombined with T cytotoxic/suppressor phenotype (CsA-Tc/s, OX8+W3/25-) in numbers contained in 100 X 10(6) CsA-T cells were ineffectual, even when supplemented with exogenous interleukin 2-rich conditioned medium (IL-2CM); in contrast 100 X 10(6) s-T cells + IL-2CM inevitably caused acute rejection in B hosts (11 +/- 3 days). Increasing numbers of Th incrementally to 100 X 10(6) augmented the effectiveness of s-Th (rejection in 13 +/- 2 days), but did not improve potency of CsA-Th (20 +/- 2 days). Suppressor activity produced by small numbers of contaminating CsA-Tc/s (c. 0.4%, 4-5 X 10(5) cells in 100 X 10(6) CsA-Th) accounted for extended graft survival in B recipients, as this small number of CsA-Tc/s transferred into untreated syngeneic rats increased test graft survival to c. 16 days (P less than 0.001). IL-2 production by spleen cells, depressed during CsA treatment, returned to normal levels 2-3 weeks following drug withdrawal, whereas transfer of CsA-Th into B recipients induced a shift of IL-2 levels from dramatically depressed to normal, findings suggesting normal IL-2 production by CsA-Th. This report demonstrates that an unresponsive state in CsA-treated animals is achieved despite the presence of fully potent donor-specific Th. Active suppressor activity plays a critical role in the maintenance phase of graft survival in rats treated transiently with CsA.

Animals↗

PubMed1985

Interleukin 2-dependent release of interleukin 3 activity by T4+ human T-cell clones.

We have isolated and studied two alloreactive, T4+, human lymphocyte clones that release interleukin 2 (IL-2) and interleukin 3 (IL-3) bioactivities upon stimulation with IL-2, alloantigen, or Sepharose-conjugated antibodies directed against the T3 protein. Anti-IL-2 receptor monoclonal antibodies block IL-2-, alloantigen-, or anti-T3-stimulated IL-3 release. Hence, release of IL-3 activity in each circumstance is rigorously dependent upon activation of the IL-2 receptor. Even low, nonmitogenic concentrations of recombinant IL-2 stimulated IL-3 release.

Cells, Cultured↗

PubMed1985

Lack of evidence for an active role for natural killer cells in acute rejection of organ allografts.

Explore the source record for details and available documents.

Animals↗

PubMed1984

Interactions between T lymphocyte subsets supported by interleukin 2-rich lymphokines produce acute rejection of vascularized cardiac allografts in T cell deprived rats.

A series of adoptive transfer studies were performed to define both the role of lymphocyte subpopulations and of lymphokines in the reestablishment of immunologic responsiveness towards vascularized organ allografts in T cell-deprived B rats. Acute rejection of otherwise indefinitely surviving cardiac allografts (10.9 +/- 2.9 days) occurred when sensitized T cells were adoptively transferred with a course of partially purified, lectin-free IL 2-conditioned medium (IL 2CM), whereas rats receiving T cells alone rejected their grafts at 19.8 +/- 4.6 days (p = 0.025). Rejection is mediated primarily by alloactivated T helper cells highly enriched for W3/25 phenotype. The relationship between the mean allograft survival time and the cell number transferred was of exponential order. In contrast to rejection occurring after the transfer of intact T cells, that produced by W3/25+ cells was independent of the administration of exogenous IL 2CM. W3/25+ T helper cells were also found to be less potent in mediating graft rejection than were whole T cells when limited cell numbers were transferred. The OX8+ T cytotoxic/suppressor cell subpopulation, even when supplied with a course of IL 2CM, was unable to bring about rejection, but induced transient graft enlargement in about 50% of the animals. Recombination of individual subsets caused acute rejection at a rate comparable to that of unseparated T cells when IL 2CM was supplied (10.8 +/- 1.0 days), in contrast to those rats which received the recombined inoculum in the absence of IL 2CM (16.8 +/- 2.2 days, p = 0.025). Lymphocyte migration studies revealed a more vigorous homing of OX8+ cells to the allograft as compared to W3/25+ cells. However, to produce maximal accumulation of transferred cells in the graft, both T cell subsets supplemented by lymphokines must be introduced together into T cell-deprived hosts.

Animals↗

PubMed1984

Cyclosporine therapy of rat heart allograft recipients and release of interleukins (IL 1, IL 2, IL 3): a role for IL 3 in graft tolerance?

LEW rat recipients of (LEW X BN)F1 strain heterotopic cardiac transplants treated with cyclosporine A (CsA) (15 mg/kg/day intramuscularly, 7 days) retain grafts indefinitely despite drug withdrawal. Donor-specific suppressor T cells that are active in passive transfer experiments have been harvested from long-term CsA-treated hosts. Although CsA is known to inhibit in vitro cytokine release, the in vivo effects of the CsA on the lymphokine cascade are not known. We investigated the action of the drug upon spontaneous and mitogen-induced interleukin 1 (IL 1), interleukin 2 (IL 2), and interleukin 3 (IL 3) release by spleen cells obtained from the following groups of rats: 1) normal, i.e., untreated and ungrafted; 2) grafted, acutely rejecting; 3) grafted, actively treated; and 4) under CsA-induced state of "tolerance." The results demonstrate that in vivo CsA therapy inhibits monocyte (IL 1 release) as well as lymphocyte function (IL 2 and IL 3 release) only during the inductive phase (the 7 days of treatment). During the "tolerant" phase, mitogen (Con A and LPS)-induced release of interleukins was quantitatively similar to that noted in normal animals. In contrast, a remarkable increase in the spontaneous production of IL 3 was observed in the "tolerant" group. Because cytokine release is not inhibited in the "tolerant" state, our data strongly support the concept that maintenance of the state of unresponsiveness is governed by the emergence of suppressor cells. The correlation of increased spontaneous production of IL 3 during this period leads us to postulate that this interleukin may be implicated in the activation or clonal expansion of suppressor cells, and hence may play a role in graft tolerance.

Animals↗

PubMedDate not supplied

Stable renal transplant recipients can be safely converted from MMF to enteric-coated mycophenolate sodium tablets: Interim results of a multicenter Latin American study.

Enteric-coated mycophenolate sodium (EC-MPS) is designed to reduce mycophenolate acid (MPA)-related upper gastrointestinal (GI) adverse events (AEs). A multicenter, open-label, Latin American study in stable renal transplant patients is ongoing to assess the safety of the conversion from mycophenolate mofetil (MMF) to EC-MPS. An interim analysis was performed when 93 patients had completed 3 months. Prior to conversion, they had received MMF at a dose of 2 g/d, with the exception of eight adult patients who were receiving an average daily dose of 1.25 g. All adult patients were converted to EC-MPS (1.44 g/d; 0.450 g/m(2) bid for children). After conversion, the reported total incidence of AEs was 40.9%, including 28% infections, 1.1% hematologic, 19.4% GI, including 10.8% upper-GI AE (all mild) and 5.4% diarrhea. No patient discontinued the study medication due to adverse events. Only six patients (6%) required a dose adjustment. There were no episodes of acute rejection, death, or graft loss. During the period of analysis, the conversion from MMF to EC-MPS was safe, the enteric-coated tablet formulation prevented release of MPA in the upper GI tract, and only one patient had to reduce the dose due to an upper GI AE, concomitant with diarrhea. EC-MPS offers transplant physicians and their patients an alternative MPA therapy that is as effective and safe as MMF, but in a formulation that may provide GI tolerability benefits.

Administration, Oral↗