B-cell subsets responsive to fluorescein-conjugated antigens. IV. Cross-stimulation of B cells genetically unresponsive to LPS by hapten-conjugated lipopolysaccharide

B-cell subsets specific for the same hapten share immunoglobulin (Ig) receptors for hapten, but presumably possess different receptors for mitogen. However, we and others recently presented evidence that B cells responsive to different forms of the same hapten (FL) could be activated to clonal expansion by a single FL-antigen, an effect called "cross-priming." Since it was critical to establish that this phenomenon was independent of putative mitogen receptors for a given FL-antigen, we attempted cross-priming of C3H/HeJ spleen cells with FL-conjugated LPS, an antigen to which they are unable to respond by either mitosis or polyclonal differentiation. Our data indicate that FL-LPS does indeed cross-prime C3H/HeJ B cells such that the subsequent response to other FL-antigens is increased. Augmentation of the anti-FL response was elicited by even nanogram doses of FL-LPS, whereas unconjugated LPS (up to 10 μg/ml) was without effect. These data suggest that induction of a positive signal in FL-responsive cells does not require an interaction with putative mitogen receptors but can occur via hapten:Ig receptor interactions.