Novel role of extracellular carbon dioxide in lymphocyte proliferation in culture

CO2/HCO3- buffering system is indispensable to maintain the pH of culture m edia for long-term cell culture. Now-a-days, the zwiterionic hydrogen buffe r HEPES is widely used as an additional buffer in the commonly used culture media. There are reports on the successful use of HEPES-buffered media, un der CO2/HCO3- free conditions, for long-term cell cultures. However, still CO2/HCO3- buffering system is widely used. We aimed at investigating the re ason for this. We found that lymphocytes proliferate in response to concana valin A only in HCO3--buffered medium in the presence of 5% CO2, but not in the HEPES-buffered medium in the absence Of CO2. However, lymphocyte proli feration was observed in HEPES-buffered medium in the presence of 5% CO2 an d in the absence of HCO3-. On the other hand, a low level proliferation was observed in HEPES-buffered medium supplemented with HCO3- in the absence o f CO2. Supplementation of the culture medium with TCA cycle intermediates a nd the precursors for the salvage pathway of nucleotide synthesis did not s upport the lymphocyte proliferation at all. Based on these findings and oth er reports, we suggest that extracellular CO2 plays a novel role in cell pr oliferation. (C) 2001 Wiley-Liss, Inc.