V-H V-L GENE-EXPRESSION IN POLYREACTIVE-ANTIBODY-PRODUCING HUMAN HYBRIDOMAS FROM THE FETAL B-CELL REPERTOIRE/

Among a panel of nearly 3,000 IgM-producing hybridomas obtained from 2 2 independent fusions of human fetal lymphocytes (liver/spleen; 15th-3 6th gestational week) a high number (5-10%) produced autoantibodies, i ndependently of the gestational age. A significant portion of these au toantibodies was found to be polyreactive, i.e. capable of binding to more than two antigens, when tested against a set of five antigens of the internal (ssDNA, thrombocytes, keratin) and external (lipid A, tet anus toroid) environment. Analyzing the IgV(H) genes utilized in eight polyreactive and two putatively nonpolyreactive hybridomas, members o f the VHI, III, IV and VI families were found once, seven times, once and once, respectively, mostly with germline identity. All but one of the utilized gene elements could be related to the biased V-H gene rep ertoire said to be expressed during the early ontogeny of the human im mune system. We also noted a bias for the utilization of DN1 (3/10), D HQ52 (3/10), J(H)2 (4/10) and J(H)6 (4/10) elements, whereas all heavy -chain CDR3 regions manifest a diversity by addition of N nucleotides and/or exonuclease activity on coding segments. In addition, V-L segme nts which belong to different subgroups of both isotypes were found to be used. The molecular basis of polyreactive immunoglobulin specifici ties in human fetuses is discussed.