NATURAL-KILLER-CELL ACTIVITY DURING UVR-INDUCED SKIN TUMOR-FORMATION IN THE SKH HAIRLESS MOUSE

We analyzed natural killer (NK) cell activity in the hairless albino S kh/HR1 mouse, to study whether the NK cell activity plays a role durin g UV radiation (UVR)-induced carcinogenesis, In 4 h Cr-51-release assa ys, spleen lymphocytes of specific pathogen-free (spf) Skh/HR1 mice di splayed 5-10% spontaneous NK cell activity, This was comparable to NK cell activity in C57Bl/6, C3H and athymic NMRI nu/nu mice, which were also kept under spf conditions, In all strains investigated, the low s pontaneous NK cell activity could be increased up to 20-30% by intrape ritoneal administration of polyinosinic:polycytidylic acid (polyI:C), a standardized in vivo NK cell induction method, The polyI:C potentiat ion of NK cells in Skh/HR1 mice was similar to that in C57Bl/6 and NMR I, but significantly less than in C3H mice, Chronic daily UV irradiati on according to a protocol that was also used for induction of carcino genesis (11-12 weeks, 95 mJ/cm(2) of UV exposure from FS40 sunlamps) d id not decrease NK cell activity on a cell for cell basis, Neither was the inducibility of NK spleen cell activity with polyI: C in Skh/HR1 mice during UV exposure reduced, Based on total organ basis, the poole d lymph node cells (axillary, mandibulary and inguinal lymph node) sho wed a doubling of NK cell activity (P < 0.001), mainly due to an almos t 100% increase in the number of lymph node cells. In conclusion, UVR does not suppress the normal or inducible NK cell activity at the time of clinical appearance of skin tumors, This suggests that such suppre ssion of NK cell activity is not likely to contribute to UVR-induced c arcinogenesis in the Skh/HR1 strain.