Characterization of CD8(+) leukocytes in fugu (Takifugu rubripes) with antiserum against fugu CD8 alpha

We have investigated the characteristics of CD8(+) leukocytes by using an anti-CD8 alpha antiserum raised in mouse by DNA-immunization. The magnetically sorted CD8 alpha(+) peripheral blood leukocyte (PBL) population comprised lymphocytes/thrombocytes and monocytes, whereas CD8 alpha(-) PBLs consisted of lymphocytes/thrombocytes, monocytes, and neutrophils. Expression analysis demonstrated that both groups of cells expressed the CD3 epsilon and TCR alpha genes. The CD8 alpha and CD8 beta genes were detected only in CD8a alpha(+) cells, whereas expression of CD4 and immunoglobulin light chain (IgL) was observed only in CD8a- cells. These results suggest that fugu CD8 alpha(+) leukocytes contain CD8(+) T cells, but not CD4(+) T cells or B cells. Furthermore, mitogenesis of the CD8(+) lymphocyte/thrombocyte population was induced by phytohemaglutinin stimulation, suggesting that fish CD8(+) lymphocytes/thrombocytes (probably CD8(+) T cells) have characteristics similar to mammalian CD8(+) T cells. Neutrophils and monocytes/macrophages infiltrating a subcutaneous inflammatory site expressed only CD8 alpha, but not CD8 beta, or, TCR alpha, or IgL. This result suggests that similar to mammalian dendritic cells, fugu monocytes/macrophages express CD8 alpha. (c) 2007 Elsevier Ltd. All rights reserved.