Humoral immune responses to tumor-specific antigens in strain-2 guinea pigs.

Abstract

Serum antibody against tumor-specific antigens on the surface of line-10 guinea-pig hepatoma cells was demonstrated by equilibrating serum with viable tumor cells and detecting bound antibody by indirect immunofluorescence. Summation of fluorescence intensity grades of individual cells led to a semiquantitative assay of antibody activity sufficiently precise for studies on the magnitude and time course of antibody response. Antibody was found not only in guinea pigs immunized against line-10 tumor with a line-10 BCG vaccine, but also in animals with progressively growing and metastasizing tumors. All animals studied had a primary humoral response to line-10 BCG vaccine and generally developed higher antibody levels after multiple inoculations of tumor cells. Immunization with line-10 antigen extracts in complete Freund adjuvant produced delayed cutaneous hypersensitivity responses, but no humoral antibody was detected until after challenge with viable tumor cells, when an apparent anamnestic antibody response was seen. Guinea pigs with progressively growing line-10 tumors developed antibody after 4-5 weeks of tumor growth. Before antibody was detected, their serum inhibited the binding of antitumor antibody to line-10 cells.