Evidence for additional subunits associated to the mouse interleukin 2 receptor p55/p75 complex.

Previous studies have indicated that high-affinity interleukin 2 receptors (IL-2R) are comprised of at least two distinct noncovalently associated subunits of Mr 55,000 (p55) and Mr 75,000 (p75). To biochemically characterize p75, we have directly isolated IL-2R using affinity precipitations with immobilized IL-2. We now report that at least some mouse p75 appears to exist as a disulfide-linked heterodimer with a subunit of Mr 22,000 (p22). These findings suggest that functional high-affinity mouse IL-2R may be comprised of at least three distinct subunits. The possibility of an even more complex structure is suggested by the coprecipitation of a protein of Mr 40,000-45,000 (p40) that may represent an additional IL-2R-associated protein.