Drug-induced immune tolerance to sheep erythrocytes in mice of different lines]

Immunological tolerance to sheep erythrocytes was induced in mice of the CBA, C57BL/6, CC57BR, C3H, DBA/2 lines by means of combined administration of a high dose of the antigen and cyclophosphamide. The count of 19S antibody-forming cells was determined in the mouse spleen after the test injection of erythrocytes, by local hemolysis in gel. The extent of the tolerance induced proved to depend on the genotype of the animals; mice of the DBA/2 line were found to be most "sensitive" to its induction. There was revealed no correlation between the level of the immunological reactivity to sheep erythrocytes in the intact mice of different lines and the extent of its suppression in tolerance induction     

Lipopolysaccharide-induced suppression of the primary immune response to a thymus-dependent antigen.

The immune response to a thymus-dependent antigen was depressed in vivo and in vitro in spleen cells from mice injected with LPS i.p. a few days before challenge with the antigen. Spleen cells from LPS-injected mice could, however, respond with increase DNA synthesis after activation with polyclonal B and T cell activators in vitro. The LPS-activated spleen cells could actively suppress normal cells in their response to the antigen sheep red blood cells. The suppressor cells contained in the LPS-activated spleens were most likely B lymphocytes, and the possible mechanism for their inhibitory function is discussed.     

Effect of antimicrobial surface-active agents on the immune response to thymus-dependent antigen in mice

The study showed that miramystin, a cationi surfactant, was an immunostimulant inducing an increase in humoral and cellular immunity in response to sheep red blood cells. The observed dose-dependent stimulating effect of miramystin on antibody production and development of DTH recommends its use as an immunologic adjuvant in the laboratory practice. It also indicated to the prospects in investigation of immunologic adjuvant properties of other preparations belonging to surface-active substances.     

Influence of a sublethal irradiation on the immune response of the mouse to sheep erythrocytes]

In the CBA mice, the immunological response of the spleen cells (RFC and PFC direct and indirect) against the sheep erythrocytes is highly depressed by a 400 R dose of X rays. The recovery is not complete at the 30th day after irradiation. The response of the bone marrow cells either irradiated or unirradiated to the antigenic stimulation is very low.     

Development of delayed hypersensitivity to sheep erythrocytes after separate and combined administration of the antigen and cyclophosphamide]

The ability to the development of delayed hypersensitivity (DHS) to the appropriate antigen was studied in mice treated with large doses of SRBC and cyclophosphamide at varying time prior to the experiment. Suppression of DHS development induced by administering either the cytostatic alone or a large dose of the antigen was examined at the same periods of time. The combined treatment was shown to induce tolerance according to diverse tests for DHS (skin and macrophage migration inhibition tests). At the basis of this tolerance lies genuine deficiency of the appropriate clone of T cells. Administration of cyclophosphamide alone leads to a slight suppression of DHS, while a large dose of the antigen induces a different form of areactivity due to the suppressor cells whose nature is not yet clear.     

Induction of oral tolerance in the primed immune system: influence of antigen persistence and adjuvant form

Oral tolerance is being promoted as a therapy for autoimmune diseases and therefore will need to be functional in a primed immune system. In previous studies, we found that although primed mice could be tolerized by feeding ovalbumin (OVA), the degree of the tolerance and its effects on individual components of the systemic immune response were more limited than that found in naive animals. Here we increased the dose and frequency of antigen feeding in an attempt to extend the effects of oral tolerance in primed mice and to understand why its effects are limited under these conditions. Increasing the amounts of OVA fed, up to a single dose of 400 mg, or using multiple feeds of 5 x 5 or 5 x 25 mg OVA, did not radically alter the extent of tolerance, with DTH responses, antigen-specific proliferation, and IL5 and IFN-gamma production still being tolerized, but antibody responses remaining generally resistant. The deficient tolerance in primed mice could not be overcome by waiting for maximum clonal expansion to wane and was not influenced by persistent release of antigen from a depot adjuvant. We conclude that the resistance of primed mice to oral tolerance may be due to the fact that antigen-experienced T cells may be inherently resistant to induction of tolerance, or that the microenvironment of the primed immune system inhibits the delivery of tolerogenic signals to antigen-specific T cells.     

Induction of allograft tolerance in the absence of Fas-mediated apoptosis.

Using certain immunosuppressive regimens, IL-2 knockout (KO) mice, in contrast to wild-type (wt) controls, are resistant to the induction of allograft tolerance. The mechanism by which IL-2 regulates allograft tolerance is uncertain. As IL-2 KO mice have a profound defect in Fas-mediated apoptosis, we hypothesized that Fas-mediated apoptosis of alloreactive T cells may be critical in the acquisition of allograft tolerance. To definitively study the role of Fas in the induction of transplantation tolerance, we used Fas mutant B6.MRL-lpr mice as allograft recipients of islet and vascularized cardiac transplants. Alloantigen-stimulated proliferation and apoptosis of Fas-deficient cells were also studied in vivo. Fas mutant B6.MRL-lpr (H-2b) mice rapidly rejected fully MHC-mismatched DBA/2 (H-2d) islet allografts and vascularized cardiac allografts with a tempo that is comparable to wt control mice. Both wt and B6.MRL-lpr mice transplanted with fully MHC-mismatched islet allografts or cardiac allografts can be readily tolerized by either rapamycin or combined costimulation blockade (CTLA-4Ig plus anti-CD40L mAb). Despite the profound defect of Fas-mediated apoptosis, Fas-deficient T cells can still undergo apoptotic cell death in vivo in response to alloantigen stimulation. Our study suggests that: 1) Fas is not necessarily essential for allograft tolerance, and 2) Fas-mediated apoptosis is not central to the IL-2-dependent mechanism governing the acquisition of allograft tolerance.     

Interrelations of cellular and humoral immune response and different doses of sheep erythrocytes in mice]

In experiments on CBA and C57BL/6 mice the generation of antibody-forming cells respectively either in the popliteal lymph nodes or spleen as well as a rate of delayed type hypersensitivity response (DTHR) on the background of subcutaneous (into foot) or intraperitoneal injection of different doses of sheep erythrocytes (from 10(4) to 10(8)) have been studied. In so doing two types of immune response can be isolated on the dependence upon the sensitivity threshold to antigen of DTHR and humoral immunity. Thus in C57BL/6 mice the antigen threshold for DTHR is of one time (in intraperitoneal immunization) or of a two times (in subcutaneous) lower order than for antibody response. In CBA line mice under subcutaneous immunization there can be seen quite an opposite picture while intraperitoneal immunization causes exact correlation of antigen threshold for cellular and humoral immune response.     

Phenotypic correction of the immune response by L-tyrosine in mice reacting oppositely to sheep erythrocytes

The possibility of transversion of low-reacting mice into high-reacting ones evaluated by the application of the natural immunostimulators. L-tyrosine and thymic polypeptides (taktivin) were compared by their ability for the phenotypical correction of the immune response of the oppositely reacting mice. It was established that under the application of L-tyrosine to oppositely reacting mice the phenotypical correction of the immune response is possible. The dramatic increase in AFC and the AFC-SI secreting IgM is observed in the mice, low-reacting to SRBC in comparison with the high-reacting lines.     

Restoration and stimulation of the in vitro immune response of B cells to sheep erythrocytes by interleukins and muramyl dipeptide (MDP)

MDP, a synthetic muramyl dipeptide, is capable of increasing the primary in vitro antibody response, to sheep erythrocytes, of purified B cells restored with a monokine and helper T cell factors, including Interleukin 2 and the late-acting T cell replacing factor (TRF). First, the possibility that the adjuvanticity of MDP could be due to the elaboration of Interleukin 1, caused by its effect on macrophages, was excluded. In addition, a kinetic study showed that the effect of MDP was greater when added later, concomitantly with or one day after the helper T cell factors. Therefore, it appears that MDP acts directly on B cells, in a late stage of their differentiation to antibody-producing cells.