The Journal of Immunology, Vol 140, Issue 12 4199-4203, Copyright © 1988 by American Association of Immunologists

ARTICLES

Characteristics of the IL-2 receptor expressed on large granular lymphocytes from patients with abnormally expanded large granular lymphocytes. Implication of a non-Tac IL-2-binding peptide

T Hori, T Uchiyama, R Onishi, M Kamio, H Umadome, S Tamori, T Motoi, T Kodaka and H Uchino
First Division of Internal Medicine, Faculty of Medicine, Kyoto University, Japan.

Large granular lymphocytes (LGL) from four patients with abnormally expanded LGL in the peripheral blood were studied regarding their receptor for IL-2. LGL from none of the cases examined expressed Tac Ag, an Il-2R glycoprotein recognized by anti-Tac mAb. However, 125I- labeled IL-2 binding experiments demonstrated that 1400 to 2800/cell IL- 2 binding sites with a single affinity (K: 0.46-1.4 nM) were expressed on LGL from the four patients. The affinity was not high but about 10- fold higher than that of the low affinity IL-2R expressed on activated normal T lymphocytes. Furthermore, LGL from the four patients proliferated in response to higher concentrations of IL-2 and these responses were not inhibited by an excess amount of anti-Tac antibody. 125I-Labeled IL-2 cross-linking studies performed in two cases revealed the predominant expression of an IL-2 binding molecule with an estimated Mr of 70,000 to 75,000. After the culture with IL-2 for 48 h, expression of a small amount of Tac Ag (p55) was induced on LGL in at least three cases. These data strongly suggested that the IL-2R expressed on LGL is functional and identical to the p70, a novel IL-2 binding peptide that has been recently identified and speculated to form the high affinity IL-2R in association with the p55.