Human basophils express interleukin-4 receptors.

Area of Science:

• Immunology
• Cell Biology
• Hematology

Background:

• Interleukin-4 (IL-4) is a key lymphokine regulating immune responses.
• IL-4 interacts with hemopoietic cells via specific cell surface receptors.
• The expression of IL-4 receptors on human basophils remains to be fully elucidated.

Purpose of the Study:

• To investigate the presence and characteristics of IL-4 binding sites on human basophils.
• To quantify the affinity and number of IL-4 receptors on primary basophils and a basophil cell line.
• To assess the functional impact of IL-4 on basophil activity and differentiation markers.

Main Methods:

• Enrichment of human basophils from peripheral blood of chronic granulocytic leukemia (CGL) donors.
• Radioligand binding assays using 125I-radiolabeled recombinant human (rh) IL-4.
• Scatchard plot analysis to determine receptor affinity (kd) and number.
• Exposure of basophil cell line KU812-F to rhIL-3 and rhIL-4 to assess receptor modulation and functional effects.

Main Results:

• Purified human basophils specifically bound rhIL-4, revealing high-affinity IL-4 binding sites.
• Quantitative analysis showed approximately 280-640 IL-4 binding sites per CGL basophil with a kd of ~7-9.5 x 10(-11) mol/L.
• The basophil cell line KU812-F expressed 810-1,500 high-affinity IL-4 binding sites per cell (kd of ~2.6-5.5 x 10(-10) mol/L).
• Neither rhIL-3 nor rhIL-4 significantly altered IL-4 receptor expression or binding constants on KU812-F cells.
• rhIL-4 did not affect histamine release, 3H-thymidine uptake, or the expression of key basophil differentiation antigens.

Conclusions:

• Human basophils express specific, high-affinity IL-4 binding sites.
• IL-4 receptor expression on basophils is not modulated by IL-3 or IL-4 under the tested conditions.
• IL-4 does not appear to directly induce proliferation, histamine release, or alter major differentiation antigen expression in human basophils.