TARGET-INDUCED ANERGY OF NATURAL-KILLER CYTOTOXIC FUNCTION IS RESTRICTED TO THE NK-TARGET CONJUGATE SUBSET

This study examined the characteristics of functional anergy of natura l killer cells (NK) following their interaction with target cells. Pur ified NK cells were cocultured with K562 for 1.5 min or 4 hr to allow for binding of targets to NK cells. The resulting NK-target conjugates were then dissociated by EDTA, and the unbound NK cells were separate d from the targets by flow cytometry and cell sorting. Compared to unt reated NK cells, the K562-dissociated NK cells were inhibited for cyto toxic function as assessed by the Cr-51 release assay and by the singl e killer frequency assay and also responded poorly following activatio n by IL-2 or IFN-alpha. The inactivated NK cells had a diminished abil ity to reform conjugates with the target cells. Following cell sorting of the NK subsets, the conjugate subset had the least cytotoxic activ ity when compared to both the free NK subset or the unfractionated NK population. The IL-2 response observed with the unfractionated anergic NK cells was found to be due to the activation of the NK free cell su bset while the conjugate subset was poorly responsive to IL-2. The cel l surface CD16, CD2, and CD56 antigen expression was downmodulated in the conjugate subset but not in the free cells. However, the CD69 surf ace expression was significantly upregulated on the surface of the NK conjugate subset and was potentiated following treatment with IFN-alph a and IL-2. These results demonstrate that target-mediated anergy of N K cells is restricted to the NR-target conjugate subset while sparing the remaining free cell subset. Further, the findings demonstrate that the anergic NK cells express the phenotype (dim)CD2(dim)CD56(dim)CD69 (bright)CD11(b)(bright). (C) 1995 Academic Press, Inc.