Receptors for histamine can be detected on the surface of selected leukocytes.

Histamine insolubilized by chemical linkage via a protein or polypeptide carrier to Sepharose beads cannot penetrate cells. Even so, the resultant histamine-coated Sepharose binds leukocytes selectively. Despite the low molecular weight of histaminie, the binding is via preformed cell membrane receptors and can be specifically and competitively blocked or reversed by antihistamines.