The Early Response of Immunocompetent Cells as Analyzed by Velocity Sedimentation Separation

Abstract

Separation of cells by velocity sedimentation is based primarily on differences in cell size. Immunocompetent cells (ICC) from mice primed for 24 to 48 hr with the polymerized flagellar antigen of Salmonella adelaide (POL) have been separated from nonreactive cells by virtue of their increased sedimentation velocity. In vitro and in vivo POL challenges of the sedimented fractions of ICC have demonstrated a depletion of reactivity in the normally immunocompetent slower sedimenting fractions and an enrichment in the normally unresponsive faster fraction. The modified velocities of ICC have returned to normal 15 weeks after the initial injection of antigen. Changes induced by POL in the sedimentation velocity of certain subpopulations of cells are specific for that antigen. The response of sedimented fractions from normal mice, when cultured with tolerogenic amounts of POL. is uniformly reduced by 75%. The profile of the immune response which remains is the same as that of cells challenged with immunogenic levels of antigen in vitro.