The proliferation and differentiation of 1)maphoid cells can be stimulated bv specific antigens, antigen-antibody complexes, plant mitogens and hormones. The initial event in the response to these diverse agents is believed to be the binding of stimulator molecules to receptors located on the cell surface (1, 2). However, the mechanism by which the binding of receptor to its ligand triggers cell differentiation and division is unknown. Prerequisite to the understanding of the cellular events occurring subsequent to surface receptor-stimulator interactions is knowledge of the nature of such receptor molecules and the manner in which they are associated with the cell membrane.We have approached the problem of identification of cell surface receptors bv developing a method based on the lactoperoxidase-catalyzed radioiodination of proteins (3), which allows covalent labeling of proteins present on the surface of lymphoid cells (4). Electron microscopic evidence indicated that only the outer surface of the cell is labeled by this method. In addition, sufficient radioactivity is incorporated into the surface to allow fractionation of iodinated proteins by a variety of techniques. This method has facilitated the isolation of immunoglobulin from the surface of mouse spleen cells (5) and human and mouse thymus cells. I Since cell viability is not adversely affected by this gentle method of iodination, physiological studies of accessible surface proteins may be carried out using living lymphocytes. The experiments reported herein demonstrate that many proteins associated with the cell surface exist in a dynamic state. We

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To determine whether perfusion preservation affected the structure and survival of kidney transplants, we correlated clinical and histologic data in 77 kidneys biopsied one hour after transplantation. Twenty-one of 36 perfusion-preserved kidneys had a glomerular capillary lesion suggestive of intravascular coagulation. None of 41 kidneys preserved by hypothermia alone had this lesion. Presence of the lesion did not correlate with donor or recipient characteristics, warm or cold ischemia time, HLA match, percentage of preformed lymphocytotoxic antibody titers or perfusion characteristics. Of 21 transplants with the lesion, nine required nephrectomy by one month, and one-month serum creatinine was less than 2.0 mg per deciliter in only three of the remaining 12 transplants. We conclude that perfusion preservation may cause pathologic changes that may adversely affect kidney-transplant function. The causes of the pathologic process remain unclear.