Immunogenetics of response to a purified antigen from group A streptococci. I. Complex segregation analysis.

A purified, extracellular protein, M. W. 17500, from group A streptococci was used in an in vitro model to study genetic aspects of immune responsiveness. Peripheral blood lymphocytes from members of eight nuclear families and one kindred of three generations were isolated and purified by F-icoll-Isopaque flotation and cultured together with varying concentrations of antigen. A summary measure of the antigen response data (measured as CPM) was constructed through a weighted regression analysis of response on dose. Commingling analysis of the standardized regression coefficients provided evidence for the existence of two underlaying distributions. Segregation analysis confirmed that response to this antigen is controlled by a major gene and is inherited in an autosomal dominant manner.