Histamine receptors on human peripheral blood leucocytes

Human blood leucocytes were tested for their capacity to bind histamine coupled as a rabbit serum albumin conjugate (H-RSA) to formalized ox red cells. The percentage of rosette-forming target cells was directly related to the concentration of erythrocyte-bound H-RSA. Under optimal experimental conditions the average number of rosettes was 52% for monocytes, 3 for lymphocytes, 25% for neutrophils and 59% for eosinophils. Free histamine partially inhibited rosette formation by blood monocytes in a dose-dependent fashion from 10-3 to 10-5 mol/l, and complete inhibition was achieved by the H-RSA conjugate. In contrast, three amines chemically related to histamine, L-histidine, imidazoleacetic acid and N-acetylhistamine, had no inhibitory effect. The histamine H1 antagonists, mepyramine and chlorpheniramine, and the H1 receptor agonist, 2-(2-aminoethyl)-thiazole, all inhibited rosette formation by blood monocytes in a dose-dependent fashion. However, the H2 receptor antagonists, burimamide and metiamide, and the H2 receptor agonists, Dimaprit and 4-methyl-histamine, were inactive. There was no statistical difference in the percentage of histamine rosettes for monocytes. lymphocytes, neutrophils or eosinophils between atopic and non-atopic individuals.