B-cell subsets responsive to fluorescein-conjugated antigens: I. Sensitivity to anti-IgD, tolerance, and cross-priming

B-cell subsets responsive to different molecular forms of the same hapten, fluorescein (FL), have been characterized in terms of their sensitivity to anti-IgD inhibition, and tolerance. The PFC responses to putative T-cell independent antigens, such as FL-lipopolysaccharide, FL-purified protein derivative, and FL-Ficoll, are inhibitable by allo-anti-δ, whereas the FL-polymerized flagellin and FL-Brucella abortus responses were not. Sensitivity to tolerance induction only partially correlated with anti-δ sensitivity, but not with T-cell independence. Thus, while the presence of IgD may signify a mature, relatively tolerance-resistant stage in a major lineage of B cells, possession of IgD, per se, does not appear to be directly responsible for the resistance to tolerogenesis which develops during ontogeny. In the presence of anti-δ and the appropriate concentration of FL- Ficoll, a form of “tolerance” may be induced in the FL-lipopolysaccharide subset. Interestingly, a low concentration of FL-Ficoll “primed” all subsets for a subsequent augmented PFC response. The latter effect was not anti-δ sensitive and suggests that antigen-IgM interaction (rather than with IgD or PBAs) is sufficient to cause B-cell expansion. Our results further substantiate the existence of B-cell subsets but indicate that stimulation to division may be elicited in all subpopulations by a single FL-antigen.