We have continued our studies of the mechanisms that regulate the activation, proliferation, and differentiation of human B lymphocytes. The cytoplasmic domain of the B-cell membrane protein CD22 has been shown to interact with three tyrosine kinases; p53 p56 lyn, p72 syk, and p85 PI-3 kinase via an ARH1 motif. CD22 has been shown to provide a B-cell activation signal and in the presence of cytokines to induce proliferation and Ig production. The interaction of CD22 with its counter receptor on T cells enhances T-cell proliferation. Several new members of the BL34 gene family have been identified. A full-length murine BL34 cDNA has been isolated and a transgenic mouse developed. A fusion protein between the extra-cytoplasmic domain BL11 and the constant region of IgG has been made for functional studies and the identification of a ligand for BL11. The GC kinase protein has been shown to have auto- catalytic activity and a GC kinase antibody localized the protein in germinal center B cells. The majority of the CD20 promoter has been in vivo footprinted. A diverged octamer binding site, a BSAP site, a likely ETS protein binding site, and several sites just proximal to the start sites are protected. Several novel DNA binding proteins have been identified by gel shift assays binding to regions of the CD19 promoter. B-cell lines deficient in CD19 have been isolated, several of which have defective BSAP expression. The CD22 promoters have been in vivo footprinted and several novel cis-elements identified. Promoter constructs have been made and will be useful for mapping the regulatory regions in the promoter. The BTK and BL34 promoters have also been isolated, the RNA start sites mapped, and promoter constructs are in the process of being made. Human genomic clones for HLX and HB9 have been isolated and the nucleotide sequence of each gene determined. The promoters for both genes have been isolated and studies of their regulation initiated. The HB9 gene has been found to be expressed in germinal center B cells and in the GI tract particularily in pancreas. Jak-3 kinase has been found highly expressed in cytoplasmic Ig+ B cells. Several monoclonal antibodies reactive with activated B cells have been characterized. A study of several transcription factors found in various B-cell subsets has identified several distinctive expression patterns. Bcl-x mRNA transcripts have been analyzed in human B-cell lines and B- cell subsets and found to be low in immature B-cell lines and germinal center B cells.
