Histamine receptors on leukocytes: the binding of histamine serum albumin conjugates is non-specific.

It is commonly held that certain leukocyte sub-populations adhere selectively to histamine-serum albumin conjugates. A large number of soluble histamine, ethylamine and dimethylaminopropylamine conjugates were synthesised and labelled with fluorescein isothiocyanate (FITC). Although a number of conjugates bound to mononuclear cells and granulocytes our data showed this binding to be non-specific. The binding of histamine conjugates to leukocytes was not inhibited by preincubation of cells with free histamine at concentrations of up to 10(-1) M nor was it pH sensitive. In addition, conjugates of ethylamine and dimethylaminopropylamine showed a similar binding pattern to that of histamine conjugates. We suggest that the observed binding may be due to modifications to the net charge of the carrier protein molecule.