| Research Abstract |
We established two monoclonal antibodies (TU27mAb and TU11mAb) specific for the human IL-2 receptor (IL-2R) beta chain. TU27mAb inhibited IL-2-binding to IL-2Rbeta but not TU11mAb. Peripheral blood leukocytes were examined for expression of the IL-2Ralpha and beta chains by two-color flow cytometric analyses using mAbs. NKH-1^+ non-T non-B cells expressed IL-2Rbeta but not IL-2Ralpha. In CD4^+T cells, IL-2Ralpha^+ cells were significantly detected, but little or marginally of the IL-2Rbeta^+ cells. However, IL-2Rbeta^+ cells were significantly detected, but little of the IL-2Ralpha^+ cells in CD8^+T cells. IL-2Rbeta^+ cells, but not IL-2Ralpha^+ cells, were also detected in CD14^+ monocytes. In CD20^+B cells, a small number of IL-2Ralpha^+ cells was detected, but little of the IL-2Rbeta^+ cells.
TU11mAb co-precipitated two molecules, p64 and p55, with IL-2Rbeta in the lysates of IL-2R-bearing cells in the presence of IL-2 even in the absence of a chemical cross-linker. The peptide maps indicate that p64 is a molecule distinct from both IL-2Ralpha and IL-2Rbeta, and that p55 is identical to IL-2Ralpha. These findings suggest that p64, along with IL-2Ralpha and IL-2Rbeta, is a component of the IL-2R complex, and we have tentatively named it the gamma-chain of IL-2R.
Using TU11mAb, we also demonstrated the IL-2-induced phosphorylation of IL-2Rbeta on tyrosine residues in IL-2-dependent T cells. The tyrosine phosporylation correlates with the IL-2-induced cell growth, and rapidly increases during the first 5 min of IL-2 stimulation. These results suggest some roles of a tyrosine kinase associated with IL-2Rbeta in the IL-2-induced signal-transductng pathway.
|
