The activation, by antigen, of naive TCR transgenic CD4 T cells cultured at physiological, rather than artificially high, frequencies more accurately reflects the in vivo activation of normal numbers of naive CD4+ T cells

The majority of in vitro studies investigating the activation of naive TCR transgenic T cells routinely employ an artificially high frequency of such cells. To assess whether employing high frequencies of TCR transgenic cells in vitro accurately reflects the in vivo activation of a normal number of T cells, we cultured between 300 and 3 x 10(6) Rag2(-/-) D011.10 T cells per well under otherwise identical conditions. We find that those T cells cultured at low frequencies proliferate more and are more potently activated, as assessed by the expression of CD44 and CD62L, each giving rise to a much larger number of cytokine producing cells, comparable to the number generated in vivo when a normal number of CD4(+) T cells are activated. The effect of T cell frequency on the level of their activation was not due to differences in MHCII or CD80/86 expression by B cells, the major ARC population present, nor to increased death of B cells in high frequency cultures. Taken together, our observations illustrate the necessity of culturing naive TCR transgenic CD4(+) T cells at a physiological frequency if one is to more accurately recapitulate the in vivo activation of naive CD4(+) T cells. (C) 2012 Elsevier Inc. All rights reserved.