A natural neonatal hybridoma autoantibody to the T200 antigen.

We report on the production and characterization of a murine hybridoma generated from neonatal (less than 24 h from birth) unstimulated BALB/c splenocytes that produces an IgG2b kappa-antibody (21G10) reacting with a cell surface Ag of murine lymphocytes. By immunoprecipitation technique we determined that the Ag recognized by autoantibody 21G10 has an apparent m.w. of 200 kDa and is present on both T and B lymphocytes but not on fibroblasts. Together with the pattern of immunoprecipitation and the cell lineage distribution we suggest that autoantibody 21G10 likely recognizes the common leukocyte Ag T200. This is further inferred by using a mutant (T200-) cell line and a reference anti-T200 mAb in immunodepletion experiments. Functionally, autoantibody 21G10 blocks (greater than 90%) the incorporation of [3H]TdR by T lymphocytes stimulated in vitro with Con A, and inhibits the production of IL-2 by these cultures. This report demonstrates the existence of autoantibodies directed against lymphocyte cell surface Ag within the natural preimmune repertoire. The implication of this finding with regard to T-B cells interaction early in ontogeny is discussed.