Suppression and enhancement of in vitro lymphocyte reactivity by factors in rat submandibular gland extracts.

The addition of crude extracts from rat submandibular (SM) glands to murine spleen and lymph node cell cultures stimulated with concanavalin A (Con A) induced either suppression (at high concentrations) or further stimulation (at lower concentrations) or further stimulation (at lower concentrations) of proliferative activity. Gel filtration of the extracts revealed that suppressive activity was due to factors of molecular weight in the 50,000-96,000 range, while stimulation was due to factors in the 13,000-35,000 molecular weight range. The suppressor activity of the higher molecular weight fractions was not due to a reduction of cell viability or of the uptake of tritiated thymidine. This was demonstrated by the fact that the addition of IL-2 to the cultures completely reversed the suppressive effect. Further fractionation of the suppressive and of the stimulatory gel filtration fractions with the chromatofocusing technique led to the identification of a single fraction with suppressor activity and of multiple discrete fractions with stimulatory activity.