Molecular associations involving CD 16, CD45 and ζ, and γ chains on human natural killer cells

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Abstract
(CD3-) and (FcRI) chains associate with CD16. the low affinity receptor for IgG (FcRIII) on human NK cells and are essential for the cell surface expression of CDI6 and for CD16-mediated effector functions. This study has investigated whether, on NK cells, molecules other than CD16 associate with , and chains, as a method of identifying other NK cell surface molecules important in NK cell function. Cell surface biotinylated NK cells were lysed in digitonin, and the lysates immunoprecipitated with mAb to CD16, , and and the immunoprecipitates analysed by SDS-PAGE. CD16 mAb co-precipitated and chains (16 and 12kD. respectively) and in addition molecules of 24. 32–35, 100, 150 and 180–200 kD. Also, C, mAb co-precipitated chain, and molecules of 24–26, 32–35. 48, 50–66, 100, 150 and 180–200 kD; and co-precipitated , chain, and molecules of 24–26, 29, 32–35, 37, 45, 49, 50–66 and 100 kD. While significant amounts of , and were co-precipitated with CD16, 10 to 12-fold more and were immunoprecipitated with their respective mAb. Furthermore, depletion of CD16 from the lysate resulted in only a partial (10–12%) depletion of , and indicating that only a relatively small proportion (10–12%) of these molecules are associated with CD16. Interestingly, substantial amounts of molecules with electrophoretic mobility similar to CD16 (50–66 kD) were co-precipitated with , and chain mAb from lysates depleted of CD16. In contrast to NK cells where I, associated with a number of different molecules, the majority of , in T cells was found to be associated only with the TCR: CD3 complex. NK cells showed a strong association between CD45, CD16 and a 33 kD molecule and often a strong association of , with CD l6, CD45 and an unidentified molecule of -150 kD. Our results show first, that CD16, and each can be efficiently labelled by cell surface biotinylation, and second, that CD16, C, and each can form a complex with each other, and with a number of additional molecules including a 33 kD molecule and CD45 potentially important in NK cell function.