Activation process of macrophages after in vitro treatment of mouse lymphocytes with dodecylglycerol

SUMMARY Alkylglycerols, inflammation products of cancerous membrane lipids, efficiently activate macrophages. A brief in vitro treatment (30 min) of peritoneal cells (mixture of non‐adherent and adherent cells) with a small amount (50 ng/ml) of synthetic dodecylglycerol (DDG) resulted in greatly enhanced Fc‐receptor‐mediated ingestion activity of macrophages. However, treatment of adherent cells (macrophages) alone with DDG produced no significant enhancement of macrophage ingestion activity, implying that macrophage activation requires a contribution of non‐adherent cells. DDG‐treated non‐adherent cells were found to generate a macrophage‐activating signal factor. Studies with a serum free‐0.1 % egg albumin‐supplemented RPMI 1640 medium revealed that a serum factor is essential for macrophage activation process. Time course analysis of stepwise transfers of conditioned media of DDG‐treated or untreated B cells and T cells revealed that DDG‐treated B cells rapidly transmit a factor to untreated T cells which yield the ultimate macrophage‐activating factor. This signal transmission among these cells for the macrophage activation process is too rapid to allow time for synthesis of inducible gene products. Thus, we hypothesized that a serum factor is modified by the pre‐existing function of DDG‐treated B cells and further modified by the pre‐existing function of untreated T cells to yield macrophage‐activating factor. This hypothesis was confirmed by the demonstration that DDG‐treated splenic non‐adherent cell ghosts modify a serum factor to yield macrophage‐activating factor.