Characterization of the role of mononuclear cell subpopulations in the in vitro lymphocyte proliferation assay.

Purified human mononuclear cell subpopulations have been evaluated in the in vitro lymphocyte proliferation assay. Monocyte-depleted mononuclear cells had reduced or absent responses to mitogens and antigens which could be restored to the original mononuclear cell response by addition of purified plastic adherent cells. Purified T lymphocytes obtained by density gradient centrifugation of E-rosette-forming cells demonstrated low but significant proliferative responses to mitogens, but no significant response to antigens. The addition of monocytes potentiated the response of purified T cells to mitogens and antigens, but did not fully reconstitute the original mononuclear cell response unless non-T lymphocytes were also present. It is concluded that mononuclear cell proliferation represents a complex mechanism of cellular interaction involving multiple subpopulations of cells.