The Effect of Antigens in Combination on Lymphocyte Transformation in vitro

Abstract

Human peripheral lymphocytes from a donor sensitized to both tetanus toxoid and smallpox vaccine were cultured in the presence of mixtures of varying concentrations of these antigens. The degree of lymphocyte transformation was measured on the 8th day by assay of the incorporation of tritiated thymidine. When both antigens were present at their optimal concentration there was no summation of the effects produced by each separate antigen. In mixtures containing a high concentration of tetanus toxoid and an optimal concentration of smallpox vaccine the stimulant effect of the latter was completely inhibited. The only circum-stances in which a summation effect was detected was that in which both anti -gens in the mixture were at concentrations considerably below their optimal. One population of lymphocytes able to recognize both antigens is present. A clonal selection mechanism which would produce 2 separate populations of lymphocytes, each sensitive to one antigen only does not seem to operate in this system.