T Cells in Fish

• Published in: Biology (Basel, Switzerland) Vol. 4; no. 4; pp. 640 - 663
• Main Authors: Nakanishi, Teruyuki, Shibasaki, Yasuhiro, Matsuura, Yuta
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI 25.09.2015; MDPI AG
• Subjects: CD4; CD8; Cytotoxicity; Review; T cells; Thymus; Cytotoxicity; CD4; T cells; CD8; Thymus
• ISSN: 2079-7737; 2079-7737
• DOI: 10.3390/biology4040640

Cartilaginous and bony fish are the most primitive vertebrates with a thymus, and possess T cells equivalent to those in mammals. There are a number of studies in fish demonstrating that the thymus is the essential organ for development of T lymphocytes from early thymocyte progenitors to functionally competent T cells. A high number of T cells in the intestine and gills has been reported in several fish species. Involvement of CD4⁺ and CD8α⁺ T cells in allograft rejection and graft-versus-host reaction (GVHR) has been demonstrated using monoclonal antibodies. Conservation of CD4⁺ helper T cell functions among teleost fishes has been suggested in a number studies employing mixed leukocyte culture (MLC) and hapten/carrier effect. Alloantigen- and virus-specific cytotoxicity has also been demonstrated in ginbuna and rainbow trout. Furthermore, the important role of cell-mediated immunity rather than humoral immunity has been reported in the protection against intracellular bacterial infection. Recently, the direct antibacterial activity of CD8α⁺, CD4⁺ T-cells and sIgM⁺ cells in fish has been reported. In this review, we summarize the recent progress in T cell research focusing on the tissue distribution and function of fish T cells.