T-lymphocyte/monocyte interaction in response to phytohemagglutinin.

Macrophage cooperation has been shown to be necessary for the thymus-derived lymphocyte to express many of its differentiated functions. The importance of macrophage-lymphocyte interaction has been extended to the study of nonimmunogenic mitogenesis. Utilizing human macrophages and T-cells prepared separately to greater than 98% purity, we have demonstrated a marked degree of dependence of the T-cell upon the macrophage for mitogenesis in response to phytohemagglutinin. The degree of dependence observed is greater than that seen with other human systems and on the order of that seen in the highly purified nonhuman systems. The nature of the physical interaction between the macrophage and the T-cell was visualized using conventional light microscopy and scanning electron microscopy. Lymphocytes were observed to form a semirosetting pattern around the macrophage very early following mitogenic stimulation. The lymphocytes were observed to proceed through early blastogenesis while in direct contact with the macrophage.