• 1 January 1980
    • journal article
    • research article
    • Vol. 42  (3) , 515-522
Abstract
Using immunofluorescence and pulse-label studies with 3H-labeled amino acids, histamine [H] was shown to inhibit the secretion of newly synthesized C2 [complement component 2], C4, C3, [complement] factor B and .beta.1H globulin by [human] monocytes in culture. Apparently protein synthesis was decreased and newly synthesized intracellular protein degradation was increased in H-treated monocytes. The observations that all monocytes in cultures containing H stained for C2, C4, C3, factor B and .beta.1H, when secretion was impaired, shows that all monocytes synthesize these proteins. A negative feedback loop on C3 and C5 cleavage is demonstrated. The anaphylotoxins, C3a and C5a, formed as a result of C3 and C5 cleavage, release H from mast cells and basophils. H, by inhibiting the production of C4, C2, C3 and factor B by mononuclear phagocytes, inhibits further C3 and C5 cleavage by restricting the formation of .**GRAPHIC**. .**GRAPHIC**. and .**GRAPHIC**.