Small B cells as antigen-presenting cells in the induction of tolerance to soluble protein antigens.

TLDR

Nonresponsiveness of helper T cells may arise when antigen is presented by small, resting B cells that lack accessory signals, leading to inactivation or deletion of T cell precursors. The study examined whether resting B cells can induce tolerance to soluble protein antigens in mice by targeting antigen specifically to B cells. Mice were intravenously injected with ultracentrifuged Fab fragments of rabbit anti‑mouse IgD (Fab anti‑delta). Fab anti‑delta treatment induced profound, antigen‑specific tolerance to Fab NRG, which was dependent on B‑cell antigen presentation, impaired T‑cell help, and reduced antibody production by B cells from treated mice. Abstract truncated at 250 words.

Abstract

We have investigated the ability of resting B cells, acting as antigen-presenting cells, to induce tolerance to soluble protein antigens in mice, using an antigen targeted specifically to B cells. We inject mice intravenously with ultracentrifuged Fab fragments of rabbit anti-mouse immunoglobulin D (IgD) (Fab anti-delta). Treatment with Fab anti-delta results in profound tolerance to challenge with 100 micrograms Fab nonimmune rabbit Ig (Fab NRG), precipitated in alum, as measured by antibody production. Tolerance to rabbit Fab is antigen specific, since the treated mice make normal antibody responses to a control antigen, chicken Ig. Tolerance is dependent on antigen presentation by B cells, since intravenous injection of soluble Fab NRG, which is not targeted to B cells, results in a much lower frequency and degree of tolerance, especially at lower doses. T cell help in this system is affected, since T cells from Fab anti-delta-treated mice fail to provide help for an adoptive primary antibody response to Fab NRG when transferred together with normal B cells into severe combined immunodeficient (SCID) mice. The antigen-specific B cell compartment is also affected during tolerance induction, since B cells from treated animals make less antibody than normal B cells when transferred into SCID mice with normal T cells. Although the mechanism of nonresponsiveness in the helper T cell compartment remains to be determined, we think it is likely that the precursors of helper T cells are inactivated or deleted by encountering antigen presented by small, resting B cells, which lack accessory signals necessary to induce helper T cell proliferation and differentiation to effector function. (ABSTRACT TRUNCATED AT 250 WORDS)