Disrupting III3 impairs production of IL-4 specified by the linked allele

Interleukin 13-deficient (IL-13(-/-)) mice express a defect in priming for IL-4 production that is not corrected by adding IL-13 to the priming cultur e. This is partly accounted for by the consumption of IL-4 without endogeno us replacement during culture of IL-13(-/-) CD4(+) T cells. We examined cel ls from mice in which disrupted Il13 was linked to wild-type Il4 on one chr omosome and wild-type Il13 was linked to a "knocked-in" green fluorescent p rotein (GfP) gene in the Il4 locus. Our results show that the deficit in IL -4 production was due, at least in part, to a cis effect, in which disrupte d Il13 diminished IL-4 production from the linked Il14 gene.