We have used sponge matrix allografts to investigate how alloantigen influences the pattern of CTL accumulation at a graft site. These studies employed two limiting dilution analysis techniques to monitor CTL accumulation. One technique quantitates the subpopulation of CTL that show evidence of in vivo contact with graft alloantigens (alloantigen-conditioned CTL or cCTL). The other quantitates all CTL with specificity for graft alloantigens, regardless of their differentiative status. Using these techniques, we have demonstrated that sponge allografts acquire three types of CTL: (a) donor-reactive CTL precursors (pCTL), (b) donor-reactive cCTL, and (c) pCTL with irrelevant antigen specificity. Sponge isografts rarely acquire LDA-detectable CTL, unless they receive a concurrent allogeneic stimulus at a distant anatomic site. In that instance, sponge isografts acquired pCTL, but not cCTL. This indicates that an ongoing immune response to alloantigens can influence the immunologic characteristics of an unrelated inflammatory response occurring elsewhere. We further observed that sponge isografts can be made to acquire alloreactive cCTL only when specific alloantigens are placed in the isograft. This indicates that specific grant