The antibody repertoire of early human B cells. II: Expression of anti-DNA-related idiotypes.

Cord blood B cells were immortalized in vitro with Epstein-Barr virus (EBV). Supernatants containing greater than 500 ng/ml IgM from clones/lines were tested for expression of anti-DNA-associated 16/6 and PR4 idiotypes (id) by ELISA. Four of 70 lines, but no clones, were positive for 16/6 id and none expressed the PR4 id. The presence of 16/6 id on four cell lines was associated with specificity for ssDNA, cardiolipin and Fc of IgG. No association was seen with binding to the K30 polysaccharide of Klebsiella. One clone binding this antigen also had anti-ssDNA, anti-Fc and anti-cardiolipin activity but did not express 16/6 id. Our data support the germ-line nature of the 16/6 id and are consistent with the notion that IgM autoantibody-producing B cells use VH genes which are part of the normal B cell repertoire.