LEUKOCYTE SUBPOPULATIONS IN DEVELOPING CARP (CYPRINUS-CARPIO L.) - IMMUNOCYTOCHEMICAL STUDIES

The distribution of leucocyte subpopulations was studied in thymus, he ad kidney, spleen, gut and blood of developing carp by using monoclona l antibodies against early T cells, B cells, thrombocytes and macropha gelike cells. In the first week post-fertilisation (p.f.), early T cel ls are very numerous (approximately 77%) in thymus, but are also prese nt in other organs, especially the head kidney; subsequently these cel ls gradually disappear in all organs, except the thymus (approximately 40%). B cells appear in head kidney from the second week p.f., and la ter in spleen and blood, but their number remains low in thymus and gu t. Thrombocytes first appear in spleen during the first week p.f. and their percentage increases until the fourth week (approximately 30%). Monocyte/macrophage-like cells are present in all organs from the firs t week p.f., and their percentage gradually increases until the eighth week p.f. This study indicates that: (1) thymus may be the primary ly mphoid organ for T lymphocytes; (2) head kidney could be the primary l ymphoid organ for B lymphocytes; (3) spleen is a primary site for thro mbopoiesis; and (4) monocyte/macrophage-like cells are already present in early age. These findings provide new information on the developme nt of the fish immune system. (C) 1997 Academic Press Limited.