C1q inhibits the expression of B lymphoblastoid cell line interleukin 1 (IL 1).
Although the existence and ubiquity of the C1q receptor is well established, its role in health and disease is largely unknown. Interleukin 1 (IL 1) is the major immunoregulatory molecule produced by macrophages and B lymphoblastoid cell lines. In this paper we present evidence that occupancy of C1q receptors by C1q on B lymphoblastoid cell lines inhibits "IL 1-like" activity, which is constitutively produced by these cells. When 5 X 10(6) Raji cells were cultured (24 hr at 37 degrees C) in the presence or absence of various concentrations of C1q (final concentration; 5 to 50 micrograms/ml) and the cellfree supernatants were analyzed for their effect on thymocyte proliferation by using the concanavalin A co-mitogenesis assay for IL 1, a statistically significant dose-dependent reduction of 3H-TdR incorporation was observed. Similar results were obtained when Daudi and Wil2WT cells were used, whereas Molt4, which is a T cell lymphoblastoid cell line, neither produced "IL 1-like" activity nor was affected by C1q. When immune complex-bound C1q was used instead of free C1q, inhibition of B cell IL 1 activity was also observed. Mixing experiments showed that Raji cells incubated with C1q released an inhibitor of IL 1-induced thymocyte proliferation. C1q alone had no effect on thymocyte proliferation in the presence or absence of human IL 1. In addition, the effect of C1q on IL 1 activity was abrogated either when the C1q was heat inactivated (56 degrees C, 60 min) or when the C1q was incubated with the cells in the presence of F(ab')2 anti-C1q. On the basis of these data, it is concluded that B cell receptor-bound C1q may play an important role in immunoregulation.
D000936:Antigen-Antibody Complex / Q000276:immunology; D001402:B-Lymphocytes / Q000378:metabolism*; D002352:Carrier Proteins; D002460:Cell Line; D003166:Complement Activating Enzymes / Q000502:physiology*; D003172:Complement C1 / Q000502:physiology*; D015922:Complement C1q; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D018960:Hyaluronan Receptors; D007375:Interleukin-1 / Q000378:metabolism*; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D008562:Membrane Glycoproteins; D024101:Mitochondrial Proteins; D011951:Receptors, Complement / Q000502:physiology
D000936:Antigen-Antibody Complex; C087299:C1QBP protein, human; D002352:Carrier Proteins; D003172:Complement C1; D018960:Hyaluronan Receptors; D007375:Interleukin-1; D008562:Membrane Glycoproteins; D024101:Mitochondrial Proteins; D011951:Receptors, Complement; C032402:complement 1q receptor; D015922:Complement C1q; D003166:Complement Activating Enzymes