Tolerogenic Capacity Research Articles

Induction of in vivo helper activity for murine antibody responses by macrophages pulsed with ovalbumin-monomethoxypolyethylene glycol (OA-mPEG) conjugates

Conjugates of protein antigens with an optimal number of monomethoxypolyethylene glycol (mPEG) chains of an appropriate molecular weight had been shown to suppress murine IgE responses to the unmodified antigen. To investigate the possibility that the tolerogenic capacity of these mPEG conjugates is attributable to a defect in macrophage (Mφ) presentation of their antigenic determinants, the activity of ovalbumin (OA)-mPEG conjugates when pulsed onto mouse peritoneal adherent cells (Mφ) was compared in this study with their activity in solution. Surprisingly, in contrast to the suppressogenic capacity of mPEG conjugates in solution, the OA-mPEG pulsed Mφ appeared to exert a helper effect when injected intraperitoneally (ip), i.e., after subsequent immunization with dinitrophenylated OA (DNP 3-OA) in Al(OH) 3, the mice showed accelerated IgE and IgGl antibody responses to OA and DNP. However, when Mφ were exposed to limiting concentrations of OA or OA-mPEG, markedly higher concentrations of OA-mPEG were required to yield pulsed Mφ, exerting a significant helper effect. It was concluded that although Mφ were capable of presenting the OA determinants of OA-mPEG conjugates to helper T (Th) cells, the preparations of modified antigen were presented less effectively than native OA.

The significance of the variety of mechanisms of allograft tolerance.

The influence of variations in protocol on the induction and early stages of maintenance of allograft tolerance in neonatal rats was studied. Allogeneic bone marrow cells, the anti-recipient activity of which was specifically reduced because of their origin from immunologically tolerant donors, possessed diminished tolerogenic capacity. This was commonly manifested by development of an unreactive state in only one of the two parameters of reactivity--allograft rejection and graft-versus-host reactivity--that were monitored. A similar deviation from the occurrence of unreactivity in both forms that characterizes tolerant rats was observed in animals which had been inoculated with syngeneic thymus cells at the time of induction of tolerance. Attempts to demonstrate a requirement for an extended period of exposure of young rats to semi-allogeneic bone marrow cells before specific unreactivity on the part of host cells became irreversible were unsuccessful.

The Induction of Hapten-Specific Immunologic Tolerance and Immunity in B Lymphocytes

Abstract The serum from mice that had been rendered specifically tolerant (TolS) to the trinitrophenyl (TNP) hapten by the injection of trinitrobenzenesulfonic acid (TNBS) was tested in vitro for its ability to induce unresponsiveness in untreated spleen cells. Conjugated with TNP at a concentration of ≈4 × 10-4 M, TolS induced complete TNP-specific tolerance in cultures of spleen cells challenged with TNP-lipopolysaccharide (TNP-LPS) and 4-hydroxy-3-iodo-5-nitrophenylacetic acid conjugated polymerized flagellin (NIP-POL). By using normal mouse serum (NMS) as a control, TNP-specific tolerance in the in vitro antibody response was induced by cultivation of spleen cells with amounts of TolS ranging from 10-4 to 10-2 ml (equivalent to 4 × 10-8 to 4 × 10-6 M TNP) in 1 ml cultures of 10 × 106 viable spleen cells. Thymic-derived (T) cells were not required for the induction of the unresponsiveness in TNP-specific bone marrow-derived (bursal equivalent, B) lymphocytes. TolS induced tolerance in cultures challenged with either T cell independent (TI) or T cell dependent (TD) forms of the TNP hapten. TolS was nonimmunogenic under the in vitro culture conditions used, and did not affect control responses. Although it was most effective when harvested 4 or fewer days after TNBS injection of donor mice, TolS exerted a tolerogenic effect if obtained as much as 2 weeks after such treatment. TolS was active across both histocompatibility and immunoglobulin allotype barriers, and also exerted its tolerogenic effect in the presence of concentrations of antigen optimal for the induction of immunity. Complete tolerance was induced by pretreatment of spleen cells with TolS and extensive washing before the addition of immunogen. Following dose response kinetics, the time required and the level of unresponsiveness induced during preincubation with TolS were directly related to the dose of tolerogen utilized. The inability of TNP-lysine to act as a tolerogen and the nondialysable nature of TolS suggested that the active component of this serum is a macromolecule and not merely TNBS. Fractionation of TolS by (NH4)2SO4 resulted in virtually complete recovery of the tolerogenic activity in the globulin (nonalbumin) fraction. Although haptenated serum γ-globulins would be present in this fraction, it is also possible that other constituents with potential tolerogenic capacity are present (i.e., various serum proteins or cell surface membrane fragments that are trinitrophenylated). The data are consistent with the suggestion that TNBS-induced tolerance in vivo is mediated by a component of TolS that is active as a tolerogen in vitro.

Role of epitope density in the induction of immunity and tolerance with thymus-independent antigens. I. Studies with 2,4-dinitrophenyl conjugates in vitro.

The effect of different degrees of conjugation of levan, dextran, pneumococcal polysaccharide SIII and the copolymer of D-glutamic acid and D-lysine with the 2,4-dinitrophenyl determinant (DNP) on the immunogenic and tolerogenic capacity of its haptenic conjugates was investigated in vitro. A strikingly uniform effect of hapten conjugation was observed despite the marked difference in the mol. wt. and structure (branched or linear) of the carrier molecules. Regarding the anti-DNP response, low density conjugates were immunogenic but not tolerogenic (even at high doses), higher conjugates were both, depending on concentration, while very high density conjugates were only tolerogenic. These results confirm and extend earlier findings made with DNP conjugates of polymeric flagellin and indicate the probable generality of this principle. Together with parallel in vivo studies (Eur. J. Immunol. 1975. 5:541), they reaffirm the importance of epitope density in the discrimination between immunity and tolerance.