Supressor activity of spleen cells during medically induced immunologic tolerance]

SRBC tolerance was induced in mice (CBA X C57BL/6) F1 by single intraperitoneal injection of 6 X 10(9) SRBC and of cyclophosphamide (100-200 mg/kg) in 44-46 hours. Spleen cells of tolerant mice obtained at various periods after the tolerance induction (in 12-26 days) failed to decrease their immune response to SRBC after administration to intact syngeneic recipients. Contrary to intact mice, tolerant animals were incapable of producing suppressor cells after a single SRBC immunization. Only when 3 additional injections of high SRBC doses (6 X 10(9)) were given to tolerant mice the spleen cells in them acquired the capacity to inhibit the immune response after administration to normal mice. It is supposed that the absence of suppressor cells in induction of the immunological tolerance by means of cyclophosphane was caused by the processes of clone elimination. Suppressor cells can originate in tolerant animals under the effect of intensive antigenic stimulation, this leading to enhancement of the tolerance state as a result of additional SRBC injections.     

MIP-2 recruits NKT cells to the spleen during tolerance induction

Peripheral tolerance occurs after intraocular administration of Ag and is dependent on an increase in splenic NKT cells. New data here show that macrophage inflammatory protein-2 (MIP-2) is selectively up-regulated in tolerance-conferring APCs and serves to recruit NKT cells to the splenic marginal zone, where they form clusters with APCs and T cells. In the absence of the high-affinity receptor for MIP-2 (as in CXCR2-deficient mice) or in the presence of a blocking Ab to MIP-2, peripheral tolerance is prevented, and Ag-specific T regulatory cells are not generated. Understanding the regulation of lymphocyte traffic during tolerance induction may lead to novel therapies for autoimmunity, graft acceptance, and tumor rejection.     

The regulatory effects of cytokines on the induction of a peripheral immunologic tolerance in mice.

Previous reports have demonstrated that injection of rIL-1 alpha into mice abrogates the ability of deaggregated human gamma-globulin (HGG) to induce a state of antigen specific immunologic tolerance in vivo. Our results demonstrate that human rIL-1 beta and a bioactive nonapeptide of human IL-1 beta inhibit the induction of tolerance to HGG suggesting that IL-1 affects tolerance induction through a noninflammatory mechanism of action because the immunoactive nonapeptide possesses only immunomodulatory properties. Further, TNF-alpha but not IL-6, cytokines with many bioactivities in common with IL-1, was found to inhibit the induction of tolerance. Therefore, it appears unlikely that IL-6 plays a role in the pathway by which either IL-1 or TNF-alpha interferes with tolerance induction. Although IL-2, IL-4, and IFN-gamma were incapable of directly affecting the induction of tolerance to HGG, it was determined that IL-4 and IFN-gamma were capable of inhibiting the ability of IL-1 to abrogate tolerance induction. It has been suggested that IL-1 induces the generation of endogenous IL-1 in vivo. Further, it has been demonstrated that IFN-gamma as well as IL-4 inhibits the synthesis of IL-1. Inasmuch as IL-4 and IFN-gamma inhibit the ability of IL-1 to abrogate tolerance induction, it appears that it is the endogenously generated IL-1 that interferes with tolerance induction. It was also determined that neither IL-4 nor IFN-gamma inhibits the activity of IL-1 which is consistent with results reported by others. Thus, results presented here suggest that the inhibition of tolerance induction to HGG by IL-1 may involve the stimulation of endogenous IL-1 synthesis.     

Cellular aspects of tolerance. I. Parameters of tolerance induction in T cells of spleen and thymus

Unresponsiveness of T cells in thymus and spleen of tolerant animals was determined by reconstitution of lethally irradiated recipients. The degree of responsiveness of these animals was assessed by antigen elimination and two types of plaque assays (liquid and agar) with different sensitivity. Unresponsiveness occurred more rapidly in T spleen cells than in thymus cells. Unresponsiveness of T cells could be induced in the spleens of thymectomized animals and in T cell repopulated thymectomized lethally irradiated recipients. Induction of unresponsiveness did not depend on proliferating bone marrow cells or on accessory cells.     

Studies on tolerance induction in vitro. I. Production of immunologically tolerant rabbit spleen cells and the transfer of tolerance to untreated cells.

Tolerance was induced in rabbit spleen cells by incubation with solubilized T2 phage (S-T2)2 at 37degrees C. Spleen cells thus treated maintained normal responsiveness to an unrelated antigen, S-SP82. Transfer of tolerance was demonstrated in in vitro in that the addition of washed tolerant cells caused suppression of the response of untreated cells to an immunogenic dose of S-T2. Evidence is presented that this suppression is not due to the transfer of tolerogenic quantities of antigen. Spleen cell populations depleted of adherent cells were still capable of being made tolerant and of transferring tolerance.     

Effect of thymectomy on induction of immunologic tolerance in the effectors of delayed hypersensitivity]

The influence of thymectomy (Tx) on induction of tolerance of delayed type hypersensitivity effectors (DHE) was examined. Tx did not interfere with induction of tolerance to sheep red blood cells (SRBC) achieved with combined injections of the massive dose of the antigen and cyclophosphamide (Cy). Tx resulted in prolongation of unresponsiveness. The injection of mice with the massive dose of SRBC alone also resulted in tolerance formation. However, this type of tolghtly depressed formation of DHE in intact but not in Cy treated mice. The results obtained are in agreement with the idea of the existence of diverse mechanisms of tolerance induction (clonic-deficient and suppressor). These data also suggest the existence of two subpopulations differing in susceptibility to Cy and Tx in DHE effectors and their precursors.     

The effect of lipopolysaccharide desensitization on the regulation of in vivo induction of immunologic tolerance and antibody production and in vitro release of IL-1

As previously reported, LPS and 8-derivatized guanosine (both generators of IL-1 release), as well as IL-1 itself interfere with the in vivo induction of tolerance to DHGG in A/J mice. In the present studies it was demonstrated that desensitization of either A/J or CBA/CaJ mice with LPS aborts the ability of LPS to interfere with the induction of tolerance to DHGG. The abrogation of the ability of LPS to interfere with tolerance by LPS desensitization is not the result of neutralization of LPS by antibody produced to LPS during desensitization. Desensitization with LPS also aborts the interference with tolerance induction by 7-methyl-8-oxoguanosine. LPS desensitization inhibits the ability of LPS and/or 7-methyl-8-oxoguanosine to both convert a tolerogenic signal to an immunogenic signal and interfere with the induction of a tolerant state to a subsequent injection of Ag. The effects resulting from desensitization may be in part attributed to the depletion of IL-1. LPS desensitization also modulates the antibody response to injection of the AG, AHGG. Desensitization with LPS markedly suppresses the antibody response to a subsequent injection of AHGG in CBA/CaJ mice. Desensitization with LPS also inhibits the anti-HGG antibody response in A/J mice, but in this strain its effect is dependent on the route of injection of AHGG. In an experiment directly comparing the responses of normal and desensitized A/J mice to either intravenous or intraperitoneal injection of AHGG, desensitization only suppressed the response in mice injected with AHGG i.p.. Desensitization with LPS also inhibits the ability of LPS to act as an adjuvant in a subsequent antibody response to AHGG. Not only does desensitization interfere with the primary antibody response to AHGG, but it also interferes with the secondary response, suggesting that the primary injection after desensitization induces a state of immunologic tolerance.     

Tolerance induction by allogeneic hematopoietic stem cells

In this issue of Cell Stem Cell, Zheng et?al. (2011) report that HSCs expressing PD-L1 display enhanced engraftment in irradiated allogeneic recipients. Independently in Nature, Fujisaki et?al. (2011) observe allogeneic HSCs persisting in proximity to regulatory T?cells in nonirradiated recipients, further connecting HSCs and immune tolerance.     

Immunological specificity and the kinetics of T-suppressor induction in the immunization of mice with allogeneic spleen

A high dose immunization of mice with gamma-irradiated allogeneic spleen cells has been shown to induce, in a recipient spleen, specific suppressor T-cells, resistant to mitomycin C, which are capable of inhibiting DNA synthesis and, to a lesser degree, the generation of killer cells in the mixed lymphocyte culture (MLC). The maximum suppressor activity is reached on days 3-6 after immunization. Both reactions are blocked mostly in those stimulator cells which bear H-2 antigens used for immunization. In contrast, DNA synthesis is inhibited only slightly, if at all, when it is stimulated in MLC by third-party cells, even if these are added to the culture as a mixture with correspoding stimulators. Unlike X-irradiated allogeneic cells, the untreated ones induce a mixture of suppressors, T-cells and macrophages, with a considerable non-specific suppression. Untreated syngenic lymphoid cells induce less active non-specific suppressors with properties of macrophages.     

Immunogenetic analysis of tolerance induction in anti-alloantigen delayed type hypersensitivity responses by portal venous pre-inoculation with allogeneic cells

The present study investigates some of the immunogenetic bases for tolerance of anti-allo-delayed type hypersensitivity (DTH) responses as induced by pre-inoculating allogeneic cells via portal venous (p.v.) route. BALB/c mice were injected with totally allogeneic C57BL/6 or H-2 incompatible BALB.B spleen cells via p.v. route. These mice not only failed to exhibit anti-H-2b DTH responses, but also abrogated the potential to generate H-2b-specific DTH responses as induced by the subsequent immunization with H-2b spleen cells via subcutaneous (s.c.) route. The p.v. presensitization with allogeneic spleen cells differing at either class I or class II of major histocompatibility complex (MHC) resulted in the tolerance induction of DTH responses to the respective allogeneic class I or class II MHC antigens. Moreover, the p.v. administration of the class I-positive allogeneic cell fraction depleted of class II-positive component into recipients differing at both class I and class II was capable of inducing anti-class I DTH tolerance. These results indicate that anti-allo-class I or class II DTH tolerance can be induced independently and that the existence of class II antigens on p.v.-presensitized cells is not necessarily required for the tolerance induction of anti-allo-class I DTH response.     

The effect of aging on the induction of tolerance in a subpopulation of B lymphocytes

The present data further demonstrate that a subpopulation of B cells which were functionally deleted during aging can be revived in vivo with 7m8oGuo. This compound is a member of a family of derivatized ribonucleosides which are potent B-cell activators and adjuvants. Using this compound as a probe to revive aged hyporesponsive B cells of CBA/CaJ mice, it was demonstrated that a subpopulation of B cells functionally deleted by the aging process can be readily tolerized by DHGG in that they fail to respond to AHGG in the presence of 7m8oGuo. It appears that this compound directly affects the B cells, since it has previously been shown that another derivatized nucleoside with identical lymphocyte-modulating properties has no effect on Th cells once they have been tolerized to DHGG. B cells stimulated by the combined effect of AHGG and 7m8oGuo were more readily tolerized in aged than in young adult mice.     

Effect of thymectomy on induction of immunologic tolerance in adult mice and on the recovery of initial immunoreactivity]

The tolerance to sheep red blood cells induced with cyclophosphamide became more profound and prolonged in mice thymectomized before or after the tolerance induction. The greatest immunocompetence depression was achieved when the operation was preformed 24 hours before the tolerogenic treatment. The results obtained confirmed the assumption that this form of tolerance was due to deficiency of a definite T-helpers clones.