| Receptor/ligand | Cell distribution/response |
|---|
| CR1/C3b, C4b | RBC, PMN, monocytes, B and T cells, clearance of immune complexes, phagocytosis, facilitates cleavage of C3b to C3dg by Factor 1 |
| CR2/C3dg | B Cells, regulate B cell proliferation |
| CR4 | PMN, platelets, B cells, leucocyte/endothelial cell interaction |
| CR3/iC3b, ICAM-1, factor Xa | PMN, monocyte, phagocytosis of microorganisms, respiratory burst activity |
| C5a | PMN, monocytes, T cells, epithelial cells,
endothelial cells, hepatocytes, fibroblasts, CNS, chemotaxis,
degranulation, hyperadherence, respiratory burst, cytokine production
(IL-6, IL-8) |
| C3a | Mast cells, eosinophils, histamine release, IL-6 production |
| C1q | PMN, monocytes, B cells, respiratory burst acitivity |
| H | B cells, monocytes, secretion of factor I, respiratory burst activity |