Quantitative Study of Cells reacting to Skin Allografts

Abstract

THE cellular response to a strongly antigenic skin allograft is biphasic. Before rejection of the graft, cellular proliferation in the regional lymph nodes is largely confined to the intermediate (paracortical) zone. Then, at the time of onset of rejection, mitotic activity develops in the outer cortical zone and germinal centres are formed; simultaneously, or a little later, plasmacytes appear in the medulla of the nodes¹. The second phase is temporally, and probably also functionally, correlated with the production of humoral antibodies directed against antigens of the skin graft donor. The function of the first phase (during which antibodies are not normally detectable in the serum) is less clear, but is probably concerned with the development of the cellular mechanism for rejecting the graft. In broad terms, this cellular mechanism may be thought to consist of the production of “sensitized” lymphocytes, which become localized in the graft and there initiate a sequence of events which culminates in the graft's destruction. The meaning of “sensitization” in this context is uncertain, but some indirect evidence^2,3 favours the possibility that the cells have on their surface specific antibody-like sites which are complementary to graft antigens. There is also one report of cells releasing haemolytic alloantibody at an early stage of the antigraft reaction⁴. We have sought direct evidence for the existence of specific receptor-carrying cells by a modification of the cluster (rosette) technique^5,6.