Selective Expression of a VH1V Subfamily of Immunoglobulin Genes in Human CD5 + B Lymphocytes from Cord Blood

Human B lymphocytes expressing the CD5 surface antigen (CD5+ B cells) constitute a subset capable of producing polyspecific antibodies recognizing a variety of selfantigens . The repertoire of antibodies produced by CD5+ and CD5 B cells is different . However, it is not yet established whether this distribution is reflected in different immunoglobulin variable region gene (IgV) use. Rearrangement of heavy chain IgV (IgV ) genes represents one of the first identifiable stages in the maturation of B cells, and occurs in a developmentally ordered fashion. The repertoire of IgV gene expression is highly restricted during fetal life but diversifies progressively after birth . A high frequency of V gene use from the relatively small V IV gene family has previously been demonstrated in human fetal liver B cells. In the present study, 102 B cell lines established by Epstein-Barr Virus-transformation of separated CD5+ and CD5 cord blood B cells, were examined for the frequency of IgV expression using monoclonal antibodies to cross-reactive idiotypes (CRI) . The results demonstrate a relatively high frequency of V IV gene use (30%) in B cells from cord blood . Furthermore, two mutually exclusive CRI associated with distinct subgroups of the V IV family are segregated in their association with either subset of B cells. One CRI is exclusively expressed in lines established from CD5 + B cells while the other is associated with lines established from CD5B cells.