ALYMPHATIC PEDICLES
Abstract
Host recognition of transplanted foreign tis sue, the afferent limb of the inunune reflex, depends, in part, on the method used to expose the host to the allogeneic antigens. For large immediately vascularized organs, such as transplanted kidneys, it is logical to assume that sensitization occurs through the leakage of antigenic material, in the fonn of cellular components or fragments, into the venous effluent from the graft. This establishes contact with the host's central lymphoid tissue directly or through reticulo-endothelia system processing (I). Another important mechanism, suggested by Strober and Gowans (2), is "peripheral sensitization" , which allows for recognition of allograft antigens by sensitive host cells as they come into contact with the endothelial surfaces of the graft. These "sensitized" lymphoid cells or macrophages, or both, then initiate a cascade of recognition steps which expands a population of effector cells capable of the ultimate destruction of the allograft. Donor leukocyte passengers in the intravascular and interstitial compart ments of the allograft may also reinforce the antigenic challenge (3) .