Impairment of natural killer cell activity in Chlamydia trachomatis infected individuals

Natural killer (NK) cell activity is impaired in Chlamydia trachomatis-infe cted patients. The mechanisms behind the altered NK functions are not clear , but data concerning NK and antibody-dependent cellular cytotoxicity (ADCC ) activity have been reported. To investigate whether this impairment is re lated to a defect at the target cell binding and/or the postbinding level, we evaluated highly purified NK cells obtained from 125 C. trachomatis-infe cted patients and compared them with 101 normal controls for their ability to kill K-562 and U-937 cell lines using a Cr-51 release assay; release tum our necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma); and kill anti-IgM preincubated P-815 cell line (ADCC activity). We found a dec rease in the lytic capability of NK cells from C. trachomatis-infected pati ents against target cell lines; decreased ability to kill bound target cell s; and low levels of released TNF-alpha and INF-gamma after incubation with U-937 cells. Taken together, these findings suggest that the impaired NK c ell reaction during chlamydial infection is related to defects both at the target and postbinding levels. However, the precise mechanisms remain to be determined. The inability to restore normal NK activity after long-term cu lture in the presence of high levels of recombinant IL-2 support the hypoth esis of an anergic process during chlamydial infection.