Pteridine formation during lectin‐induced lymphocyte activation

After iodine oxidation, biopterin, 6‐hydroxymethylpterin, and 6‐formylpterin were identified in mouse spleen lymphocytes by means of reverse‐phase HPLC, Crithidia assay, and oxidative degradation. Concanavalin A activation induces a 30‐fold increase in the pteridine amounts; biopterin as well as the sum of the carbinol and the aldehyde attain levels of 6–8 × 10 −12 mol/10 6 cells. The most rapid increase occurs during the first 24 hr. Thus, pteridine accumulation precedes the period of lymphocyte proliferation; maximum DNA synthesis was found after 72 hr. Biopterin remains largely inside the cells, whereas 6‐hydroxymethylpterin and 6‐formylpterin were found in the supernatant if the stimulated cells were subsequently incubated in a phosphate buffered salt solution (PBS). Isoxanthopterin was found in the PBS supernatant of control cells that previously were kept in medium alone rather than subjected to lectin stimulation. Only minimal amounts were found inside these cells, and this pterin was absent from the stimulated lymphocytes. The early increase in cellular pteridines and their differential release may well provide the basis for their modulating effect on interleukin‐2 activity (Ziegler I, et al: Lymphokine Research 3:284, 1984).