Effect of histamine on monocyte complement production. II. Modulation of protein secretion, degradation and synthesis.
Using immunofluorescence and pulse-label studies with 3H-labelled amino acids, histamine was shown to inhibit the secretion of newly synthesized C2, C4, C3, factor B and beta 1H globulin by monocytes in culture. The findings suggested that protein synthesis was decreased, and that the degradation of newly synthesized intracellular protein was increased in histamine-treated monocytes. The observations that all monocytes in cultures containing histamine stained for C2, C4, and C3, factor B and beta 1H, when secretion was impaired, shows that all monocytes synthesize these proteins. These results demonstrate a negative feedback loop on C3 and C5 cleavage. The anaphylotoxins, C3a and C5a, formed as a result of C3 and C5 cleavage, release histamine from mast cells and basophils. Histamine, by inhibiting the production of C4, C2, and C3 and factor B by mononuclear phagocytes, inhibits further C3 and C5 cleavage by restricting the formation of C42, C423b and C3bBbP.
D000596:Amino Acids / Q000378:metabolism; D002478:Cells, Cultured; D003175:Complement C2 / Q000378:metabolism; D003176:Complement C3 / Q000378:metabolism; D003180:Complement C3b Inactivator Proteins / Q000378:metabolism; D003181:Complement C4 / Q000378:metabolism; D011415:Complement Factor B / Q000378:metabolism; D003165:Complement System Proteins / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006632:Histamine / Q000494:pharmacology*; D006801:Humans; D009000:Monocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism
D000596:Amino Acids; D003175:Complement C2; D003176:Complement C3; D003180:Complement C3b Inactivator Proteins; D003181:Complement C4; D006632:Histamine; D003165:Complement System Proteins; D011415:Complement Factor B