Shared idiotypic determinants on B and T lymphocytes reactive against the same antigenic determinants. II. Determination of frequency and characteristics of idiotypic T and B lymphocytes in normal rats using direct visualization.

Anti-idiotypic antibodies made against the antigen-binding receptors of T lymphocytes for a given antigen (Ag-B locus antigens in rats) can be shown to react with IgG antibodies of the same antigen-binding reactivity. Using such anti-idiotypic antibodies, normal Lewis T lymphocytes of B and T type can be visualized by the use of anti-(Lewis-anti-DA) antibodies. Visualization was made possible by the use of direct fluorescent antibody tests or by autoradiography. Using the first technique and naked eye observations 6.2% of normal Lewis T lymphocytes expressed idiotypic markers signifying anti-DA reactivity, whereas anti-DA-reactive B lymphocytes as measured by this approach was in the order of 1.1%. Autoradiography was purified normal Lewis T lymphocytes gave similar figures. When comparing the intensity of fluorescence at the single cell level using quantitative cytofluorometry anti-idiotypic antibodies reactive with T lymphocytes gave a similar degree of intensity as was obtained using anti-Ig antibodies against B lymphocytes.