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P Valent, J Besemer, K Kishi, F Di Padova, K Geissler, K Lechner and P Bettelheim
I. Medical Department, University of Vienna, Austria.
Interleukin-4 (IL-4), a multipotential lymphokine reputed to play an
important role in the regulation of immune responses, interacts with a
variety of hemopoietic target cells through specific cell surface membrane
receptors. The present study was designed to investigate whether human
basophils express IL-4 binding sites. For this purpose, basophils were
enriched to homogeneity (93% and 98% purity, respectively) from the
peripheral blood of two chronic granulocytic leukemia (CGL) donors using a
cocktail of monoclonal antibodies (MoAbs) and complement. Purified
basophils bound 125I-radiolabeled recombinant human (rh) IL-4 in a specific
manner. Quantitative binding studies and Scatchard plot analysis revealed
the presence of a single class of high affinity IL-4 binding sites (280 +/-
40 sites per cell in donor 1 and 640 +/- 45 sites per cell in donor 2) with
an apparent dissociation constant, kd, of 7.12 x 10(-11) +/- 2.29 x 10(-11)
and 9.55 +/- 3.5 x 10(-11) mol/L, respectively. KU812-F, a human basophil
precursor cell line, was found to express a single class of 810 to 1,500
high affinity IL-4 binding sites with a kd of 2.63 to 5.54 x 10(-10) mol/L.
No change in the numbers or binding constants of IL-4 receptors was found
after exposure of KU812-F cells to rhIL-3 (a potent activator of basophils)
for 60 minutes. No effect of rhIL-4 on 3H-thymidine uptake, release or
synthesis of histamine, or expression of basophil differentiation antigens
(Bsp-1, CD11b, CD25, CD40, CD54) on primary human CGL basophils or KU812-F
cells was observed.
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| Copyright © 1990 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
