PRODUCTION OF A MONOCLONAL-ANTIBODY THAT DEFINES THE ALPHA-SUBUNIT OF THE FELINE IL-2 RECEPTOR

A mAb, termed 9F23, to feline Con A-stimulated PBMC was prepared to characterize feline IL-2R. 9F23 was identified by FACS studies, which showed that the antigen was expressed at a high density on Con A-induced feline T cell blasts while 9F23 binding was not detected on nonactivated PBMC or the Crandell feline kidney cell line CRFK. Chemical crosslinking of 1251-IL-2 to membrane IL-2Rs on ConA-stimulated feline PBMC under the low-affinity condition resulted in detection of a major 65-kDa band. 9F23 specifically immunoprecipitated the IL-2.IL-2Ralpha complex in a cell extract; in contrast, neither anti-human 1L-2Ralpha H48 nor anti-mouse IL-2Ralpha 7D4 reacted with the complex. Moreover, immmoprecipitation with 9F23 of the extract from surface-iodinated Con A-stimulated PBMC showed a major 50-55 kDa band. Furthermore, 9F23 had no effect on either IL-2-driven proliferation of the Con A-stimulated PBMC or IL-2 binding. Finally, the expression of feline IL-2Ralpha on Con A-stimulated PBMC was up-regulated by addition of exogenous IL-2. Thus, 9F23 defines an epitope different from the IL-2 binding site on the alpha-subunit of feline IL-2R.