NZB serum factor (NZB-SF)-B precursor cell maturation factor: II. In vivo effects of NZB-SF or mAb against NZB-SF on B lineage cell populations

Abstract

In vivo effects of NZB serum factor (NZB-SF), which enhances the maturation of B precursor cells in vitro, were examined. Immunoaffinity-purified NZB-SF from young NZB mice was injected into B6 mice intraperitoneally twice weekly, five times total (5 μg/dose/mouse). Control mice were given 0.01% albumin. Then the B lineage cell populations defined phenotypically (sIg + cells, B220 + cells, and AA4.1 + cells) or the numbers of colony-forming B lineage cells were examined. NZB-SF-treated B6 mice exhibited a decrease in the percentage of B precursor cells in marrow, even though the percentage of sIg + cells in marrow or spleen did not differ from controls. In contrast, the frequency of colony-forming B cells in marrow and spleen, especially sIg + colony-forming B cells in marrow, increased significantly in NZB-SF-treated mice as compared to controls. In addition, monoclonal antibody (mAb) against NZB-SF was injected weekly for 9 weeks into NZB mice beginning at 7 weeks of age. mAb vs NZB-SF at a dose of 5 μg per mouse per injection, as stated above, prevented the decline of sIg + colony-forming B lineage cells which usually occurred in the adult NZB mice (>16 weeks). This treatment also prevented, in part, the decline of the B220 + cell population which normally occurs in the marrow with increasing age. Thus NZB-SF impressively influences the composition of B lineage cell populations in normal B6 mice and may account for abnormal changes of B lineage cell populations observed in NZB mice.