B-LINEAGE CELL DEFICITS IN BONE-MARROW OF LPR LPR MICE/

Analyses of bone marrow (BM) lymphocytes in C57BL/6 mice homozygous fo r the lpr mutation (B6.lpr) disclosed low numbers of pre-a and a cells , as compared with age-matched control B6 mice. BM depletion in B6.lpr mice was selective for a-lineage cells, appeared in young adults, and developed markedly with age and disease progression, contrasting with the peripheral lymphocyte hypercellularity. Normalization of pre-a an d a cellularity in BM of B6.lpr mice was observed after administration of polyclonal Ig, that also markedly improved the clinical condition. Isolated pre-a (B220(+) IgM(-)) cells from B6 or B6.lpr mice, however , showed essentially the same rates of IL-7-dependent proliferation an d differentiation to B (IgM(+)) cells in culture, indicating that the BM B-lineage deficit is not the result of an intrinsic defect in a cel l generation.