Human plasma-like medium improves T lymphocyte activation

T lymphocytes are critical effectors of the immune system and the ability to study their behavior in synthetic media in vitro has facilitated major discoveries in their development, function, and fate. Recently, it has been shown that the constituents in human plasma differ markedly from commonly used synthetic media and these differences have important effects on cell physiology. We therefore compared T lymphocyte activation in human plasma-like medium (HPLM) to RPMI conventional medium both with and without serum. We found that HPLM and RPMI induced vastly different transcriptional programs, especially for transcripts encoding proteins involved in activation, proliferation and metabolism, in human peripheral blood T cells after T cell receptor (TCR) stimulation. We also found that in dialyzed fetal bovine serum (dFBS), HPLM supports a stronger response to TCR engagement compared to RPMI. In reconstruction experiments, we demonstrated that this activation difference is due to RPMI being hypocalcemic relative to the in vivo milieu and that addition of calcium chloride to RPMI can improve human T lymphocyte activation. Thus, we conclude that investigators should be cognizant of differences between commonly used media formulations and the in vivo environment since this could profoundly affect their experimental results and that physiologic media is a valuable new way to study immune cells in culture