Immunogenetic analysis of proteins ofParameciumV. Detection of specific determinants in strains lacking a surface antigen

Several stocks ofParamecium aureliathat had never expressed an E serotype were examined for E-reacting material. The regular presence of the cross-reacting antigen G in these stocks ruled out the use of hapten inhibition and other standard immunological techniques. Consequently, a genetic approach was attempted in which hybrids of the E-deficient strains and non-E stocks were bred, and antigen isolated and tested for the existence of molecules with a specificity differing from that of the E-containing parent. Gel diffusion analysis suggested that E antigen from a hybrid indeed could differ from the ‘normal’ E. One of these hybrid clones which behaved as though its E antigen may have possessed a determinant contributed by the E-deficient strain was used as an immunizing antigen. The antibodies elicited possessed specificity unique for the hybrid. Thus the possession of E-like determinants by E-deficient stocks was confirmed.