Synergistic effects on DNA synthesis of phytohemagglutinin or concanavalin A and lipopolysaccharide in human peripheral blood lymphocytes.

Mixtures of phytohemagglutinin (PHA) or Concanavalin A (Con A) and lipopolysaccharide (LPS) with human peripheral blood lymphocytes (PBL) resulted in a synergistic effect on DNA synthesis as measured by increased 3H-thymidine uptake. These data were compared to the mitogenic response of human PBL to PHA, Con A, or LPS alone. Various combinations of PHA and Con A usually suppressed DNA synthesis in human PBL. Titration experiments revealed that increasing amounts of LPS, in the presence of a constant amount of Con A, resulted in corresponding increases in the synergistic response of human PBL. Conversely, increasing amounts of Con A, in the presence of a constant amount of LPA did not lead to increases in the amount of synergism. The results are discussed in terms of the participation of additional cells in the synergistic response of human PBL.