by using this two-step design , it was shown ( a ) that thymus , but not bone marrow , contained antigen-reactive cells ( arc ) capable of initiating the immune response to srbc ( first step ) , and ( b ) that the same antigen complex that activated thymic arc was required for the subsequent interaction between thymus-derived and marrow cells and/or for pfc production ( second step ) .
C0301872
immune response
C0003320
arc