Characteristics of the effector cells mediating cytotoxicity against antibody-coated target cells. I. Phagocytic and non-phagocytic effector cell activity against erythrocyte and tumour target cells in a 51Cr release cytotoxicity assay and [125I]IUdR growth inhibition assay

Both phagocytic and non-phagocytic effector cells were able to kill rabbit antibody-coated chicken erythrocytes (CRBC) while only non-phagocytic effector cells were active against alloantibody-coated SL2 lymphoma. In addition to the variation in susceptibility of erythrocyte and tumour target cells to various effector cell populations, it was found that different tumour cells can vary markedly in their ability to be killed by non-immune spleen cells in the presence of antibody. It is postulated that both the type of antibody and certain characteristics of the cell membrane are important in determining whether target cells are susceptible to antibody-dependent cell-mediated cytotoxicity detected by the 51Cr release assay. It was also demonstrated that alloantibody-coated P-815-Y mastocytoma, which showed very little evidence of cytotoxicity in the 51Cr release assay, was markedly inhibited in its ability to incorporate [125I]IUdR after incubation with antiserum and non-immune spleen cells. This growth inhibition in the absence of cytotoxicity, or cytostasis, is discussed in relation to the potential mechanisms of target cell damage, and in the light of recent observations (Plata, Gomard, LeClerc and Levy, 1974; Newlands and Roitt, 1975) that cytotoxicity and growth inhibition assays detect different effector cell populations in tumour-bearing animals.

Serum immunoreactive parathyroid hormone and 25-hydroxyvitamin D in patients with uremic bone diseases

Bone histologic parameters and serum iPTH and 25-OHD were measured in 20 patients with end-stage renal failure treated with hemodialysis. By bone histologic criteria, the patients were divided into three groups: mild, osteomalacic, and fibrotic. The increase in serum iPTH was much greater in the fibrotic group than in the mild or osteomalacic groups. In the uremic patients as a group, there were significant correlations between serum iPTH and both percent marrow fibrosis and percent resorbing surface. In the mild and fibrotic groups together, serum iPTH was also correlated with percent forming surface. This and other findings suggested that most of the bone changes in the mild and fibrotic groups could be explained by excess PTH. The difference in bone changes and in serum iPTH between the mild and fibrotic groups could be related to our eariler findings that duration of renal disease was much greater in the fibrotic than in the mild group. The lowest increment in serum iPTH was found in the osteomalacic group. In this group, percent resorbing surface was not increased and there was only a slight increase in marrow fibrosis. Thus in all three groups, serum iPTH appeared to reflect parathyroid status. The cause of the elevated serum iPTH and for the intergroup differences was not apparent inasmuch as serum calcium was normal in all three groups. Serum 25-OHD was significantly elevated in the osteomalacic and fibrotic groups. Because none of our patients had received preparations containing vitamin D, the elevated serum 25-OHD in the osteomalacic and fibrotic groups is consistent with altered vitamin D metabolism in these two groups. There was a direct relationship between percent osteroid area and serum 25-OHD. However, whether or not altered vitamin D metabolism contributed to the mineralization defect in uremic bone disease could not be established.

Characterization of the antibody-dependent cytotoxic cell. A non-phagocytic monocyte?

Death of antibody-coated chicken erythrocytes (CRBC) mediated by nonphagocytic cells was studied. The distribution of effector cells in mouse spleen lymphoid populations after fractionation by velocity sedimentation on Ficoll gradients, isopycnic centrifugation on BSA gradients, and affinity chromatography on Sephadex-linked anti-Fab columns was followed. Cytotoxicity corresponded closely with the distribution of the non-phagocytic monocytes. The cytotoxic effector cell showed similar characteristics to monocytes with respect to size, surface adherence properties and binding affinity for immunoglobulin subclasses.