An X-linked locus influences early serum interferon levels in the mouse.

There are sexual differences in early (2-3 h) interferon (IFN) production induced by NDV in the mouse, in that circulating IFN levels are higher in females than in males. From a Mendelian analysis carried out in BALB/c and C57BL/6 mice, it can be concluded that early IFN levels are quantitatively influenced by an X-linked locus, with different alleles in C57BL/6 and BALB/c. As a result of these distinct alleles, the IFN levels of the male progeny of the reciprocal F1 crosses were significantly higher when the X-chromosome was of C57BL/6 origin than when it was of BALB/c origin. The difference in early IFN production between males and females is detectable after puberty only, which indicates that sexual maturation factors influence, in the male, the expression of the X-linked locus. These observations point to differences between early and late IFN production in response to NDV. As reported earlier, there is no effect of sex on late (6-9 h) IFN production, which is under the influence of the autosomal If-1 locus. The results presented here show that whereas late IFN production is very radiosensitive, early IFN production, on the contrary, is radioresistant, indicating that different cell populations are involved in early versus late IFN synthesis.