Percentage dynamics of CD4-1+ and CD8α+ T cells in different tissues at various developmental stages in ginbuna crucian carp Carassius auratus langsdorfii.

Determination of numbers of T cell subsets in tissues is important to assess the functional maturity of the immune system. The distribution of T cells in lymphoid tissues during ontogenic development has been examined in several fish species using pan-T cell markers. However, information on the age-related changes in the number of T cell subsets in tissues is limited due to the lack of antibodies against CD4 and CD8 in fish. In the present study we examined the percentage dynamics of CD4-1 and CD8α cells in various tissues accompanied with age of ginbuna crucian carp using flow cytometry. We found rapid increases in both CD4-1 and CD8α T cells up until 6 months post-hatch (mph). CD4 and CD8 double-positive cells (DP cells) are present only in the thymus and DP cells increased, while double negative cells decreased, in fish up to 3–6 mph. The percentages of CD4-1 T cells were always higher than those of CD8α T cells in the various tissues examined, except for the thymus and intestine. In contrast, significantly higher percentages of CD8α T cells than CD4-1 T cells were found in the intestine during the period between 6 mph and 2 years post-hatch.