Complement component C3 secretion by mouse macrophage-like cell lines

Secretion of complement component C3 by the mouse macrophage-like cell lines PU5-1.8, J774A.1, RAW264.7, and P388D1 was measured using an enzyme-linked immunosorbent assay for mouse C3. All cell lines secreted antigenically detectable C3 with the relative secreted C3/10(6) cells/24 h ranked as J774A.1 greater than P388D1 greater than or equal to PU5-1.8 much greater than RAW264.7. C3 secretion was enhanced two- to fourfold in cultures of all cell lines when treated with lipopolysaccharide, streptococcal cell walls, or lymphokine-containing supernatant fluids of mitogen-stimulated spleen cells. A differential induction of C3 synthesis and secretion was indicated since secreted lysozyme and total cellular protein were not elevated in a manner comparable to C3. The relative inducibility of cell lines for C3 secretion in either lipopolysaccharide- or cell wall-treated cells could be ranked as PU5-1.8 greater than P388D1 greater than J774A.1 greater than RAW264.7. C3 secretion was inhibited by cycloheximide or hydrocortisone. Mouse macrophage-like cell lines retain baseline and inducible C3 synthetic activities as do normal macrophages and can serve as homogeneous cultures in which to study regulation of complement biosynthesis.