Ontogeny of the immune system in carp (Cyprinus carpio L.). The appearance of antigenic determinants on lymphoid cells detected by mouse anti-carp thymocyte monoclonal antibodies.

Mouse anti-carp thymocyte monoclonal antibodies were used to investigate the appearance of lymphoid cell determinants in young carp. Determinants detected by clone WCT 4 were present on thymocytes as soon as the thymus was visible histologically, day 4 after fertilization (a.f.) at 21 degrees C, but WCT 4-positive lymphocytes were not present in the pronephros until day 7 a.f.. In contrast, determinants detected by monoclonal antibodies from clones WCT 8 and WCT 10 appeared on thymocytes from day 7 a.f. at 21 degrees C, and WCT 8-positive and WCT 10-positive lymphocytes were not detected in the pronephros until days 16 and 12 a.f., respectively. These results are discussed in relation to the appearance of determinants detected by anti-carp serum immunoglobulin antisera.