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

Analyses of bone marrow (BM) lymphocytes in C57BL/6 mice homozygousfor the lpr mutation (BS.Ipr) disclosed low numbers of pre-Band B cells, as compared with age-matched control B6 mice. BMdepletion in B6.lpr mice was selective for B-lineage cells,appeared in young adults, and developed markedly with age anddisease progression, contrasting with the peripheral lymphocytehypercellularity. Normalization of pre-B and B cellularity inBM of B6.lprmice was observed after administration of polyclonalIg, that also markedly improved the clinical condition. Isolatedpre-B (B220⁺ IgM^–) cells from B6 or B6.lpr mice, however,showed essentially the same rates of IL-7-dependent proliferationand differentiation to B (lgM⁺) cells in culture, indicatingthat the BM B-lineage deficit is not the result of an intrinsicdefect inB cell generation.