Specific Activation of the Bone Marrow-derived Lymphocyte by Antigen Presented in a Non-multivalent Form

Antigen-induced activation of bone marrow-derived (B) lymphocytes involves interactions between specific antigenic determinants and immunoglobulin receptors on the lymphocyte surface (1). Soluble antigens such as serum proteins can trigger B lymphocytes only if thymus-derived (T) cells are provided (2), thus implying a requirement for some element besides a simple antigen-receptor interaction. Triggering may result from the presentation to the B cell of a mult ivalent configuration of identical antigenic determinants produced on, or through the action of, the T cell (3, 4). Alternatively, it has been postulated that, as well as the binding of antigen by receptors, the B cell must react with a second substance, this second signal being some product of collaborating T cells (5). The first hypothesis has been supported by the observation that antigens not requiring T cell help to activate B cells share a common polymeric structure (3, 6), enabling them to directly form multiple receptor-antigen bonds. The experiments to be reported offer an alternative explanation for the role of one such thymus-independent antigen, polymerized flagellin (POL) (6) in B cell triggering. They suggest that mult ivalent presentation of antigen is not an absolute requirement for B cell activation by demonstrating that antigen presented in a nonmult ivalent form can trigger B cells in the absence of T cells, under at least one circumstance.