Extracellular pH Affects the Proliferation of Cultured Human T Cells and Their Expression of the Interleukin-2 Receptor

Abstract

Ex vivo expansion of T cells is an important aspect of many cellular immunotherapy protocols, and the effects of the culture environment on the cells must be understood to produce large numbers of functional cells. Extracellular pH is a fundamental parameter that has many different effects on cultured cells. In this study, peripheral blood mononuclear cells were stimulated with phytohemagglutinin and cultured at pH values of 7.0, 7.2, or 7.4. The effects of pH on the cells were studied during the 2 to 3 weeks of proliferation resulting from phytohemagglutinin stimulation, in order to examine the culture kinetics over realistic time scales for ex vivo expansion. The proliferation capacity of the T cells increased more than three-fold for the pH 7.0 and 7.2 cultures compared with the pH 7.4 cultures. The culture pH also affected the kinetics of the interleukin-2 receptor down-regulation process. The faster receptor down-regulation in both the pH 7.2 and 7.4 cultures resulted in a more than twofold greater fraction of interleukin-2 receptor(+) cells in the pH 7.0 cultures. Although the fraction of apoptotic cells (using the Annexin V flow-cytometric method) remained less than 10%, we observed 27% more apoptosis in the pH 7.4 cultures than in the 7.2 cultures and 49% more apoptosis in the pH 7.4 cultures than in the 7.0 cultures. These effects on interleukin-2 receptor expression and cellular apoptosis may partially explain the observed effects of pH on T-cell proliferation.

Haematopoietic Culture Systems

“…The expression of G-CSF receptor was enhanced at pH 7.22 and decreased with a concomitant increase in pH (Hevehan 2000). Similarly, expression of the IL-2 receptor, critical for T-cell proliferation, was optimal at pH 7.0 and decreased in a more alkaline environment (Carswell 2000).…”

“…Gradients of pH affect the ex vivo expansion of HSCs (Akatov 1985), cell physiology and receptor expression (Carswell 2000;Hevehan 2000) as well as cell differentiation (Carswell 2000;Endo 1994;Fischkoff 1984;Hevehan 2000;McAdams et al 1997;McAdams et al 1998;Tennant 2000;Yang 2002). The optimum pH is dependent on the haematopoietic cell lineage (Table 3) (Carswell 2000;Endo 1994;Fischkoff 1984;Hevehan 2000;McAdams et al 1997;McAdams et al 1998;Tennant 2000;Yang 2002).…”

“…The optimum pH is dependent on the haematopoietic cell lineage (Table 3) (Carswell 2000;Endo 1994;Fischkoff 1984;Hevehan 2000;McAdams et al 1997;McAdams et al 1998;Tennant 2000;Yang 2002). For example, T cells proliferate better at pH 7.0-7.2 (Carswell 2000) whereas erythroid differentiation is best at pH 7.6 (Endo 1994;McAdams et al 1997;McAdams et al 1998). An increase in the population of benzidine positive cells, suggesting erythroid lineage, was also noted by examining the synergistic effect of pH 7.54 and compounds such as hemin and BSA that induce the differentiation of erythroid cells (Endo 1994).…”

“…The differentiation, maturation Ref. (Carswell 2000)2} (Endo 1994;McAdams et al 1997;McAdams et al 1998)5} (Hevehan 2000;McAdams et al 1997)3} (Fischkoff 1984 (polyploidisation), and apoptosis of megakaryocytes (CD41 + cells) was enhanced in the presence of pH of 7.4-7.6 (Yang 2002), whereas the differentiation of CFU-GM was optimal at pH 7. 2-7.4 (McAdams et al 1997).…”

An Overview on Bioreactor Design, Prototyping and Process Control for Reproducible Three‐Dimensional Tissue Culture

“…An overlay of different metabolite and factor microgradients forms distinct niches for cell differentiation, activation or energy. The differentiation and activation of hematopoietic stem cells and mature lymphocytes is biased by distinct levels of factors, such as glucose, lactate, dissolved oxygen, and pH [96,97,[100][101][102]. APC immobilized in the ECM form a cellular network and secrete chemokines for the attraction of highly migrational T lymphocytes [109][110][111].…”