T Cell-Derived Antigen-Specific Humoral Immune Response: II. Further Characterization of the Response and the Antigen Binding T Cell Immunoproteins

Murine T lymphocyte-derived proteins which bind nominal antigen specifically (TABM) were detected in serum during a humoral immune response to bovine serum albumin. The TABM response was observed only when the adjuvants polyadenylic:polyuridylic acid complex (poly(A:U)), Freundʹs complete adjuvant or Titermax were used concurrently with antigen to immunize. When poly(A:U) was used, higher doses of antigen were optimal to stimulate TABM production than those required to stimulate immunoglobulin production. The binding of TABM in the serum of BSA-immunized mice to BSA in solid phase was inhibited specifically by 10-fold more BSA than that required to inhibit BSA-specific immunoglobulins suggesting that TABM have much less affinity for antigen than immunoglobulins. Immunoblotting of TABM in serum From BSA-immune mice, which bind BSA, demonstrated that these serum TABM are comprised of Mr 110,000 polypeptides linked by disulfide bonds. Antigen-specific proteins in a lysate of an NP-specific T cell hybrid inhibited the recognition of serum TABM by anti-TABM antiserum while a lysate of a B cell hybridoma was not inhibitory, and serum TABM were adsorbed by monoclonal antibodies to TCR-Cβ. These results provide more evidence that serum TABM may be a soluble analogue of the T cell receptor for antigen.