Activation of murine lymphocytes by 2-mercapto-ethanol and related thiol compounds and its mechanism. II. Effect of thiol compounds on the viability of the lymphocytes under a cystine-deficient culture condition.

When murine lymphocytes were cultured in a cystine-deficient RPMI-1640 medium containing 10% fetal calf serum, approximately 70% of the cells died in 48 h. In the presence of 5 X 10(-4) M L-cystine, 70-80% of the lymphocytes remained viable under the same condition. The decrease of the viability was also effectively inhibited when cystine was replaced by the following thiol compounds; 2-mercaptoethanol (2-ME), dithiothreitol (DTT), cysteamine and glutathione (GSH). Oxidized DTT, an intramolecular disulfide that was resistant to the reduction by the lymphocytes, did not show a protective effect in contrast to DTT. On the other hand, 2-hydroxyethyldisulfide was readily reduced to 2-ME by the lymphocytes and improved lymphocyte viability as effectively as 2-ME. These observations suggest that thiol groups are responsible for the improvement of lymphocyte viability under a cystine-deficient condition. The viabilities of both T cells and B cells were equally improved by 2-ME. The intracellular level of GSH remained constant in the presence of cystine but dropped rapidly in its absence. 2-ME could not reverse this decrease of GSH level. These protective effects of thiol compounds on lymphocyte viability are discussed in relation to their capacities to activate murine lymphocytes.