Lymphocyte reactivity to “T” and “B” cell mitogens in Xenopus laevis: Studies on thymus and spleen

Abstract

The in vitro proliferative response of Xenopus thymus and spleen cells to the lymphocyte mitogens concanavalin A (Con A), phytohaemagglutinin (PHA) and bacterial lipopolysaccharide (LPS) was compared in serum-free and foetal calf serum (FCS) — supplemented media. Dose-response curves with Con A were comparable for thymocytes and splenocytes. Increase in the level of FCS supplementation necessitated the addition of more mitogen to achieve optimal stimulation and resulted in poorer stimulation indices, particularly in spleen cultures. Thymus and spleen also behaved similarly to each other when stimulated with PHA. Splenocyte reactivity to this mitogen was optimal under serum-free conditions or with 1% FCS supplementation. In contrast, thymocyte reactivity to PHA remained unaffected by serum addition. Splenocytes in serum-free conditions responded particularly well to high doses of LPS. Thymocyte reactivity to this and another putative B cell mitogen, purified protein derivative of tuberculin (PPD), was generally low. However, thymocytes in 10% FCS displayed significant stimulation. Thymocyte reactivity to LPS could be detected in late larval life. The possibility that some lymphocytes functionally-equivalent to mammalian B cells develop within the anuran thymus is discussed in the light of these experiments.