Disrupting Il13 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 culture. This is partly accounted for by the consumption of IL-4 without endogenous replacement during culture of IL-13 −/− CD4 + T cells. We examined cells from mice in which disrupted Il13 was linked to wild-type Il4 on one chromosome and wild-type Il13 was linked to a “knocked-in” green fluorescent protein ( 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 disrupted Il13 diminished IL-4 production from the linked Il4 gene.