Possible involvement of Ly-1 B cells in the effector phase of IgG suppression mediated by suppressor T cell factor

The effector phase of IgG suppression mediated by an antigen-specific suppressor T cell factor (TsF) was studied. The monoclonal TsF of an inducer type derived from a KLH-specific suppressor T cell hybridoma (34S-704) suppressed IgG response mounted by DNP-primed B cells (anti-Thy-1 treated spleen cells) and KLH-specific cloned helper T cells only in the presence of unprimed Thy-1-, Ly-1+, I-J+, Ig+ cells. The addition of naive Ly-1+ cells to the culture of DNP-primed Ly-1/Thy-1 depleted B cells and KLH-Th clones augments anti-DNP IgG responses, and KLH-TsF suppressed the enhanced parts of IgG responses. The Ly-1+ cell seems to be a target of TsF, because naive spleen cells treated either with anti-Ly-1 or with anti-MIg failed to absorb TsF, whereas TsF activity was absorbed with whole spleen cells and anti-Thy-1 treated spleen cells. The functional role of Ly-1 B cells and possible mechanisms in the effector phase of TsF-mediated IgG suppression will be discussed.