Ontogeny of B and T cells in sea bass (Dicentrarchus labrax, L.).

Monoclonal antibodies specific to sea bass Ig heavy (WDI 1) and light (WDI 3) chains and T cells (DLT15) were used in an ontogenetic study of sea bass by flow cytometry and immunocytochemistry. The influence of weight and age, as well as season, on B cell development was studied in the fastest and slowest growing offspring from the same spawn (5-305 days post hatch: dph). Additionally, B and T cell development was followed in samples of different offspring (5-137 dph). The results suggest that DLT15 recognises very early (pre-?) T cells as well as mature T cells and that these very early T cells might have their origin in a different compartment and subsequently mature in the thymus. They also appeared much earlier in ontogeny (between 5-12 dph onwards) than pre-B cells having cytoplasmic Ig (from 52 dph onwards). With the monoclonal antibodies used, adult levels of T and B cells were both reached between 137-145 dph, suggesting that sea bass is immunologically mature from at least that age onwards. As in other teleosts, the thymus appears to be the primary organ for T lymphocytes and head kidney the primary organ for B lymphocytes. For sea bass, age seems to be more important in determining B cell maturation than body weight.