B-lineage cell deficits in bone marrow of lpr/lpr mice.

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