Pleiotropic effects of the Bcg gene. II. Genetic restriction of responses to mitogens and allogeneic targets.

Five cell lines that express one of five isoforms of the human leukocyte common Ag (CD45) were established by transfecting a murine pre-B cell line with leukocyte common Ag cDNA constructs. Using these cell lines, the specificities of CD45 and CD45R mAb were examined. Of the 43 mAb tested, 25 antibodies recognized sequences common to all five isoforms, 16 antibodies recognized isoforms that include exon A encoded sequences, one antibody recognized isoforms that include exon B encoded sequences, and one antibody recognized only the isoform that does not include either exon A, B, or C encoded sequences. The response of Bcgr and Bcgs spleen cells to allogeneic Ag, mitogens, and in a system of oxidative mitogenesis using neuraminidase and galactose oxidase was investigated in two Bcg congenic systems. The Bcgr macrophages supported the MLR across H-2 barrier much better than the Bcgs macrophages. At sub-optimal or optimal doses of mitogens Bcgr mice were higher responders than their Bcgs counterparts. The superior response of Bcgr spleen cells to Con A was further investigated with the aim of identifying the population expressing this phenotype. T cells of either Bcgr or Bcgs type showed equal ability to respond to Con A in the presence of macrophages. Purified splenic macrophages from Bcgr mice contained a significantly greater percentage of Ia+-bearing macrophages compared to Bcgs mice. Splenic macrophages of the Bcgr type were more efficient than their Bcgs counterparts at restoring the Con A response of accessory cell-depleted spleen cells. Resident peritoneal macrophages as well as splenic dendritic cells from Bcgr and Bcgs mice were equally efficient at restoring this response. Glutaraldehyde-fixed Bcgr splenic macrophages were shown to be more efficient than the Bcgs cells at replenishing the response of Con A-unresponsive spleen cells when supplemented with IL-1.