The two major subsets of T lymphocytes, helper and cytotoxic T cells, are defined by expression of CD4 and CD8 glycoproteins, respectively. T cells expressing the CD4 surface antigen facilitate B-cell maturation and production of antibodies by B-cells and are thus termed "helper" T cells. CD4+ helper T cells recognize exogenously derived peptides in the context of MHC class II molecule expressed on antigen presenting cells. One (D1) of four Ig-like extracellular domains of CD4 primarily interacts with the α2 and β2 domains of the MHC class II heterodimer. This antibody, raised against antigens from Ginbuna carp, permits flow cytometric and immunofluorescence analysis of CD4 helper T cells from zebrafish, goldfish and the cyprinid fish carp.

Source: Dr. Teruyuki Nakanishi, Department of Veterinary Medicine, Faculty of Materials Science and Technology, University of Japan

References:
1) Toda H., et al. Conservation of characteristics and functions of CD4 positive lymphocytes in a teleost fish. Dev Comp Immunol. (2011) 35 (6), 650-660.
2) Shibasaki Y., et al. Kinetics of CD4 + and CD8α + T-cell subsets in Graft-Versus-Host Reaction (GVHR) in Gimbuna crucian carp Carassius auratus langsdorfii.

The two major subsets of T lymphocytes, helper and cytotoxic T cells, are defined by expression of CD4 and CD8 glycoproteins, respectively. T cells expressing the CD4 surface antigen facilitate B-cell maturation and production of antibodies by B-cells and are thus termed "helper" T cells. CD4+ helper T cells recognize exogenously derived peptides in the context of MHC class II molecule expressed on antigen presenting cells. One (D1) of four Ig-like extracellular domains of CD4 primarily interacts with the α2 and β2 domains of the MHC class II heterodimer. This antibody, raised against antigens from Ginbuna carp, permits flow cytometric and immunofluorescence analysis of CD4 helper T cells from zebrafish, goldfish and the cyprinid fish carp.

Source: Dr. Teruyuki Nakanishi, Department of Veterinary Medicine, Faculty of Materials Science and Technology, University of Japan

References:
1) Toda H., et al. Conservation of characteristics and functions of CD4 positive lymphocytes in a teleost fish. Dev Comp Immunol. (2011) 35 (6), 650-660.
2) Shibasaki Y., et al. Kinetics of CD4 + and CD8α + T-cell subsets in Graft-Versus-Host Reaction (GVHR) in Gimbuna crucian carp Carassius auratus langsdorfii.