In vivo activity of affinity-purified helper factor from antigen-specific helper clone

Supernatant from culture of a virally transformed OVA-specific helper T clone (C-41) was examined for the presence of soluble helper factor. Inoculation of helper clone supernatant into DNP-KLH-primed mice enhanced the IgG anti-DNP response when given with DNP-OVA. The C-41 supernatant did not trigger the DNP-primed B cells in mice when injected with hapten (DNP) coupled to an unrelated carrier (BSA). The carrier-dependent helper activity of C-41 supernatant in vivo demonstrates the presence of an antigen-specific T helper factor in the media of the cultured helper clone. Extensive immunization of F₁ (C57BL x BALB/c) mice with the helper clone resulted in the production of anti C-41 antibodies. Monoclonal antibodies prepared from the immunized mice were screened for specificity of binding to other transformed T lines and clones, some specific to OVA. Monoclonal antibodies that stained the C-41 cells exclusively were considered clone-specific. Supernatants of the helper clone were passed over columns of anti-clone-specific antibodies. The eluates from three antibodies were active as antigen-specific helper factor, i.e., they elevated the IgG anti-DNP response in vivo in a linked recognition fashion in the presence of DNP-OVA. The affinity-purified factor was inactive when injected with DNP-BSA or DNP-BSA + OVA. Thus, we describe the antigen-specific immune function of a clone-produced helper factor in normal mice.