Functional heterogeneity of nonresting B cells in human blood

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Abstract
Among human peripheral blood B cells we localized the precursors of two interleukin‐dependent B cell activation processes: the specific response to a particulate antigen, trinitrophenylated polyacrylamide beads (TNP‐PAA) and the polyclonally induced response to pokeweed mitogen. In both cases the precursors belong to the OKB7+, sIgD−, mouse red blood cell− subpopulation. However, they differ when cell density, reflecting the stage of activation reached by B cells in peripheral blood, is considered. Only B cells of intermediate density respond to TNP‐PAA, whereas the optimal response to pokeweed mitogen is obtained with the cells displaying the lower density. The lack of response of the more dense (resting) B cells to TNP‐PAA suggests that the T dependency of this antigen is not based on linked recognition, and fits with our demonstration that this particulate antigen can trigger B cells in the presence of T cell factor. More importantly, our results show that nonresting B cells are functionally heterogeneous according to their degree of preactivation: the responsiveness to specific signals provided by a nonmitogenic hapten‐carrier conjugate would be acquired before that to polyclonal activators.