Isolation and characterization of C4-synthesizing cells from guinea-pig spleen.

Separation of C4-synthesizing cells from the spleen has been achieved through isopycnic density gradient centrifugation of spleen cells on albumin gradients. Cells which synthesize C4 are low-density, large mononuclear cells, probably macrophages. C4-synthesizing cells clearly differ in density from cells which synthesize antibody to sheep erythrocytes 7 days following immunization with erythrocytes. These cells are much denser than cells which synthesize C4. Spleen cells which transfer delayed hypersensitivity to tuberculin are separated in the same region of the gradient as cells which synthesize C4, but it is considered unlikely that the two functions are associated with the same cell type.