Single-step immunosorbent preparation of F-protein from mouse liver with conservation of the allo-antigenic site, and determination of concentration in liver and serum.

A single-step immunopurification procedure is described for murine protein F, in which the T-cell-defined allo-antigenic site on the protein is fully conserved. The procedure is based on the use of a newly developed monoclonal antibody. The protein is isolated as a 42,500 mol. wt (F.1) and a 43,000 mol. wt (F.2) monomer. The content in liver, as estimated by radioimmune inhibition assay, is 0.083% and the yield is approximately one third. An assay of immunogenic activity in adoptive transfer, which detects the T-cell-defined site, provides a similar estimate of content in liver. The adoptive transfer assay yields concns of F-protein in serum of young mice of 0.5-1.2 X 10(-9)M, the lowest concn of protein known to induce complete immunological tolerance.