Human chromosomes 6 and 21 are required for sensitivity to human interferon gamma

The human interferon gamma receptor has previously been assigned to chromosome 6. Chromosome 6 also encodes HLA, the human class I major histocompatibility antigens. However, the presence of chromosome 6 in hamster-human hybrids is by itself insufficient to confer sensitivity to human immune interferon as measured by the induction of human HLA. Human chromosome 21 was found to be the second chromosome essential for HLA inducibility. Similar results were found with mouse-human somatic cell hybrids. Thus, at least two steps are involved in the action of human interferon gamma: the binding of interferon gamma to its receptor coded by chromosome 6 and the linkage of this binding event through a factor coded by chromosome 21 to trigger biological action. Both of these steps are species-specific.