A new rat monoclonal antibody (5A2) directed against the mouse interleukin 2 receptor (IL 2R) is described. This antibody binds specifically to IL 2R+ cells, competes with both cold IL 2 and 125I-labeled IL 2 for the IL 2-binding site and inhibits IL 2-induced T cell proliferation. This reagent was compared to five previously characterized rat monoclonal antibodies directed against the p55 subunit of the mouse IL 2R. The capacity of all the antibodies to inhibit IL 2-induced T cell proliferation was assessed. The relationship of these eight antibodies to each other and to the IL 2-binding site was studied by cross-inhibition assays, and by Scatchard analysis of the data. The results indicate that the six monoclonal antibodies recognize epitopes in three areas of the p55 subunit of the mouse IL 2R. Antibodies against two of the clusters affect IL 2 binding. One cluster defined by 3 antibodies is probably located in the area of the IL 2-binding site as there is competitive inhibition between IL 2 and antibodies against this cluster. A single antibody directed against an epitope outside this cluster appears to inhibit IL 2 binding by inducing a conformational change in the p55 subunit of the IL 2R. Two other antibodies identify a third region which is not involved in the formation of the binding site.
ASJC Scopus subject areas
- Immunology and Allergy