IMMUNOBIOLOGY Functional comparison of thymic B cells and dendritic cells in vivo

mouse model in which we targeted gene expression specifically to B-lympho-cytes. Using the human CD19 promoter, we expressed major histocompatibility complex class II I-E molecules specifi-cally on B cells of all tissues, but not on other cell types. If only B cells expressed I-E in a class II-deficient background, positive selection of CD41 T cells could not be observed. A comparison of the frequencies of I-E reactive Vb51 and Vb111 T cells shows that I-E expression on thymic B cells is sufficient to nega-tively select I-E reactive CD41 T cells partially, but not CD81 T cells. Thus partial negative but no positive selection events can be induced by B-lymphocytes in vivo. (Blood. 2000;95:2610-2616) r 2000 by The American Society of Hematolog