Objective: To detect the factors responsible for the susceptibility of cervical keratinocytes infected with human papillomavirus (HPV) to non-specific lysis mediated by natural killer (NK) and lymphokine activated killer (LAK) cells.
Materials and methods: Five cervical keratinocyte lines: CaSki, SiHa, HeLa (representing high grade squamous intraepithelial lesion (HSIL) ), W12 (representing low grade squamous intraepithelial lesion (LSIL) ) and NCx, (normal cervix) were used as target cells in the four-hour lactate dehydrogenase (LDH) release cytotoxicity assay. The effector cells were NK and LAK. The modulatory effects of interferon gamma (IFN gamma) and tumor necrosis factor alpha (TNF alpha) pretreatment of keratinocytes were investigated by adding IFN gamma or TNF alpha into the flasks of target cells 48 hours before the cytotoxicity assays. The blocking effects of anti-intercellular adhesion molecule-1 (ICAM-1) and anti-lymphocyte function-associated antigen-1 (LFA-1) monoclonal antibodies (Mabs) were also studied.
Results: All the 5 cervical keratinocytes were susceptible to LAK, but not to NK. The sensitivity varied among the cell lines. LAK had better killing effects on HSIL than on LSIL. Pretreatment of target cells with IFN gamma and TNF alpha increased the killing mediated by LAK, but had little effect on NK activity. Anti-ICAM-1 and anti-LFA-1 Mabs inhibited LAK-mediated cytotoxicity.
Conclusions: All the HPV infected keratinocytes used in the experiments are NK-resistant and LAK-sensitive cells. IL-2, IFN gamma and TNF alpha play some critical roles in the regulation of the susceptibility of cervical keratinocytes, especially HSIL to LAK-mediated cytotoxicity in vitro.