in a series of in vitro helper t cell assays we confronted the various t populations with b cells preimmunized with the native antigen , and we tested their capacity to help production of ( a ) binding antibodies and ( b ) antibodies directed to single conformational epitopes , characterized by their capacity to protect the enzyme from heat denaturation or to activate defective beta-galactosidase .
C0003320
antigen
C0003316
epitopes