IN-SITU LYMPHOCYTE APOPTOSIS IN LARVAL XENOPUS-LAEVIS, THE SOUTH-AFRICAN CLAWED TOAD

During Anuran metamorphosis larval structures regress, adult structure s form anew and impaired T cell immune functions are noted, as are alt erations in endogenous glucocorticoid titers. In situ histological dat a, after staining for DNA fragmentation, reveal patterns of lymphocyte suicide in the thymus and spleen of nonantigenically challenged, labo ratory bred, developing larvae, that do not correlate with either impa ired immune functions or plasma glucocorticoid titers. Apoptotic level s in the thymus are high in premetamorphic stages, low during prometam orphosis and high again, after metamorphic climax, reflecting a period ic removal of thymocytes. Lymphocytic apoptosis in the spleen is low d uring premetamorphosis, rises in prometamorphic stages, principally wi thin the red pulp, reaching a peak at climax, before declining as meta morphosis is completed. (C) 1998 Elsevier Science Ltd. All rights rese rved.