Human blood basophils synthesize interleukin-2 binding sites
H Stockinger, P Valent, O Majdic, P Bettelheim and W Knapp
Institute of Immunology, University of Vienna, Austria.
Recent data suggest that basophils express receptors for a variety of
lymphokines. In this study we present the biochemical characterization of
the interleukin-2 (IL-2) receptor on the basophil surface membrane. Highly
enriched populations (purity: 92% to 99%) of blood basophils were obtained
from chronic granulocytic leukemia (CGL) patients (n = 3) by negative
selection using monoclonal antibodies (MoAbs) and complement. CGL basophils
were found to bind CD25 MoAbs (n = 4) directed against different epitopes
of the 55- to 60-Kd subunit of the IL-2 receptor (= Tac peptide).
Immunoprecipitation experiments with lysates of purified CGL basophils and
CD25 MoAbs showed a protein with a molecular weight of 60 Kd, equivalent to
the Tac peptide on human T blasts. Quantitative binding studies and
Scatchard plot analysis using radiolabeled recombinant human (rh) IL-2
indicated the presence of 12,000 +/- 4,700 low affinity IL-2 binding sites
(kd = 66 nmol/L) per purified CGL basophil. Northern blot analysis with
enriched CGL basophils showed two messenger RNA bands of 3.5 and 1.5
kilobases hybridizing to radiolabeled Tac cDNA. Immunoprecipitation of the
Tac peptide from enriched basophils metabolically labeled with 35S-
methionine showed active synthesis of the IL-2 receptor. Our results show
that human blood basophils synthesize and express receptors for IL- 2.
Volume 75,
Issue 9,
pp. 1820-1826,
05/01/1990
Copyright © 1990 by The American Society of Hematology
