Defective natural killing activity but retention of lymphocyte-mediated antibody-dependent cellular cytotoxicity in patients with the X-linked lymphoproliferative syndrome.

Cellular mediated immune responses in vitro of six males with X-linked lymphoproliferative syndrome (XLP) were investigated. Impaired natural killing (NK) activity compared to seven controls (P less than 0.001) and interferon-alpha activation (P less than 0.011) were detected. However, normal numbers of lymphocytes expressing NK-associated antigens (Leu-7 and MO1) and large granular lymphocytes (LGL) were observed in all patients. Normal lymphocyte-mediated antibody-dependent cellular cytotoxicity (ADCC) (P less than 0.531) was found. NK and ADCC activities have been regarded as being mediated by the same subsets of lymphocytes, however, results of this study do not support this hypothesis: lymphocytes with impaired NK but normal ADCC functions (NK-/K+) were found in males with XLP.