SUSCEPTIBILITY TO IMMUNOSUPPRESSION BY ULTRAVIOLET-B RADIATION IN THE MOUSE

Irradiation with ultraviolet B (UVB; 290-320 nm) initiates systemic immunosuppression of contact hypersensitivity (CHS). UV dose-responses for suppression of CHS to trinitrochlorobenzene were established in 18 strains of inbred mice. Three phenotypes with significantly different susceptibilities to UV suppression were identified. The phenotypes were: high (HI) susceptibility, 50% suppression with 0.7-2.3 kJ/m(2) UV (C57BL/6, C57BL/10, and C57L and NZB females); low (LO) susceptibility, 50% suppression with 9.6-12.3 kJ/m(2) UV (BALB/c, AKR, SJL and NZW), and intermediate (INT) susceptibility, 50% suppression with 4.7-6.9 kJ/m(2) UV (DBA/2, C57BR, C3H/HeJ, C3H/HeN, CBA/N and A/J). UV suppression was not correlated with skin pigmentation or with the magnitude of the CHS response in non-irradiated animals. Major histocompatibility complex (MHC) haplotype was not correlated with UV suppression in MHC congenic strains B10.D2/oSnJ, B10.D2/nSnJ, B10.BR/SgSnJ, and A.BY/SnJ. There were no sex differences in UV suppression in BALB/c, C57BL/6, or NZW animals. In the autoimmune NZB strain, however, male mice (LO) were seven times less sensitive to UV suppression than NZB female mice (HI). Both sexes of (NZB x NZW)F-1 and (NZW x NZB)F-1 mice were HI, supporting dominance of HI over LO. Thus there are genetic factors and interacting sex-limited factors determining susceptibility to UV suppression. These findings may be of relevance to UV-related diseases such as photosensitive lupus and skin cancer.