Characterization of CD8+ leukocytes in fugu (Takifugu rubripes) with antiserum against fugu CD8α

SummaryWe have investigated the characteristics of CD8+ leukocytes by using an anti-CD8α antiserum raised in mouse by DNA-immunization. The magnetically sorted CD8α+ peripheral blood leukocyte (PBL) population comprised lymphocytes/thrombocytes and monocytes, whereas CD8α− PBLs consisted of lymphocytes/thrombocytes, monocytes, and neutrophils. Expression analysis demonstrated that both groups of cells expressed the CD3ε and TCRα genes. The CD8α and CD8β genes were detected only in CD8α+ cells, whereas expression of CD4 and immunoglobulin light chain (IgL) was observed only in CD8α− cells. These results suggest that fugu CD8α+ 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 CD8α, but not CD8β, CD4, TCRα, or IgL. This result suggests that similar to mammalian dendritic cells, fugu monocytes/macrophages express CD8α.