Activity and Phenotype of Natural Killer Cells in Peptide Transporter (TAP)-deficient Patients (Type I Bare Lymphocyte Syndrome)

In this paper we describe the function and phenotype of natural killer (NK) lymphocytes from HLA class I–deficient patients. These cells are, as has been previously reported, unable to lyse HLA class I⁻ K562 cells, but are able to perform antibody-dependent cellular cytotoxicity (ADCC), although with lower efficiency as compared to NK cells from normal individuals. Transporter associated to antigen processing (TAP)⁻ NK cells proliferate when cultured in the presence of lymphoblastoid B cells (B-LCs) and interleukin 2 and develop a spectrum of cytotoxicity similar to that of activated normal NK cells. Importantly, activation of the TAP⁻ NK cells induces strong cytotoxicity to autologous B-LCs. Analysis of the phenotype of circulating TAP⁻ NK lymphocytes showed them to display a normal diverse repertoire of HLA class I–specific NK receptors. These receptors were expressed at normal levels, apart from the CD94–NKG2A complex, which appeared to be overexpressed. This latter finding could reflect an adaptation to the low expression of HLA class I molecules. Finally, functional analyses indicated that the inhibitory receptors in TAP⁻ individuals can transduce inhibitory signals. Our results suggest that in vivo, the NK cells of TAP⁻ patients could participate in immune defense, at least through ADCC, but upon activation, may be involved in autoimmune processes.