Generation of stable monocyte-derived dendritic cells in the presence of high concentrations of homologous or autologous serum: influence of extra-cellular pH.

Recent studies have highlighted the high degree of differentiation of monocytes. Indeed, dendritic cells (DC) can be generated from monocytes, in the presence of appropriate cytokines. However, human serum is usually avoid in such cultures. Here, we report that human serum does not inhibit generation of mature DC from blood monocytes, but rather that extra-cellular pH may play an important role in the regulation of monocyte differentiation. Indeed, monocytes cultured at pH 7.4 in the presence of high concentrations of human serum developed efficiently into mature DC, as opposed with monocytes cultured at pH 7. These pH 7.4 cultured DC presented features characteristic of mature DC, at the phenotypical, functional and morphological levels. In addition, these DC were stable, with respect to their sustained expression of CD83 and CD86, upon withdrawal of cytokines. Finally, when autologous plasma was used instead of homologous serum, differentiation of monocytes into mature DC was efficient, as well. Thus, altogether, our data show the importance of extra-cellular pH on differentiation of monocyte-derived DC in the presence of human serum, which should be maintained at plasma levels.