In vitro production of interleukin-2 by lymphocytes in whole blood and isolated culture.

Interleukin-2 (IL-2) production was examined in mitogen stimulated human lymphocytes. Whole blood unseparated lymphocytes or Ficoll-Hypaque gradient purified lymphocytes were cultured. Lymphocytes in whole blood culture produced significantly greater amounts of IL-2 on a per cell basis than did Ficoll-Hypaque purified lymphocytes. Furthermore, the majority of IL-2 produced by lymphocytes in whole blood culture was shown by freeze-thaw lysis to be intracellularly located, while the majority of IL-2 produced by purified lymphocytes was detected extracellularly. The addition of 2-mercaptoethanol (2-ME) resulted in enhanced extracellular production of IL-2 in whole blood and Ficoll-Hypaque cultures. The use of whole blood culture, while not permitting a precise in vitro dissection of the cellular mechanisms governing IL-2 production, may more accurately reflect the mechanisms governing in vivo lymphocyte activation.