TISSUE-ASSOCIATED PHENOTYPIC HETEROGENEITY OF PERIPHERAL B-CELLS IN MICE

After their primary differentiation and selection in the bone marrow, the cells of B lineage are distributed to the peripheral lymphoid syst em. Here we report that. with the use of a novel rat monoclonal antibo dy (IBL-2), a tissue-related phenotypic difference could be observed i n the peripheral B-cell compartment in mouse. The antigen recognized b y this antibody is a 25 000/29 000 MW heterodimeric cell surface molec ule which is resistant to phosphatidylinositol-phospholipase C treatme nt, but is sensitive to proteases. The antigen was found to be express ed by the majority of B cells from the spleen, whereas the B cells fro m other peripheral sources (lymph nodes and Peyer's patches) proved to be negative. The staining pattern of splenic B cells was heterogeneou s, containing a substantial dim population (IBL-2(lo)), and a smaller, intensely stained fraction (IBL-2(hi)) within the positive subset. Un like the B cells, the T cells were negative in every peripheral lympho id tissue analysed. In addition, the ratios between the various IBL-2- reactive B cells (positive to negative and, within the positive popula tion. the IBL-2(lo) to IBL-2(hi), respectively) in the spleen were qui te similar to that of B cells in the bone marrow. Furthermore, the lev els of L-selectin expressed by the various IBL-2-reactive subpopulatio ns were found to be heterogeneous both in the bone marrow and in the s pleen. The bone marrow cells could be resolved into double negative, L -selectin(+/-)/IBL-2(lo), L-selectin(-)-IBL-2(lo), and L-selectin(-)/I BL-2(hi) populations, respectively. In the spleen, an additional fract ion with L-selectin(+)/IBL-2(-) phenotype could he detected. In both t issues, the overwhelming majority of IBL-2(hi) cells were found at the MEL-14(-) compartment. We conclude that either these findings may ref lect a heterogeneous development state within the peripheral B-cell po ol, with a substantial fraction of splenic B cells being less differen tiated than those in other peripheral lymphoid tissues, or alternative ly, the differential reactivity of murine B cells with the IBL-2 monoc lonal antibody is due to their tissue location.