Abstract
In higher vertebrates, helper and cytotoxic T cells, referred to as CD4 and CD8 T lymphocytes, respectively, are mainly associated with adaptive immunity. The adaptive immune system in teleosts involves T cells equivalent to those found in mammals. We previously generated monoclonal antibodies (mAbs) against olive flounder (Paralichthys olivaceus) CD4 T cells, CD4-1 and CD4-2, and used these to describe the olive flounder’s CD4 Tcell response during a viral infection. In the present study, we successfully produced mAbs against CD8 T lymphocytes and their specificities were confirmed using immuno-blotting, immunofluorescence staining, flow cytometry analysis andreverse transcription polymerase chain reaction (RT-PCR). The results showed that these mAbs are specific for CD8 T lymphocytes. We also investigated variations in CD4 and CD8 T cells populations, and analyzed the expression of immune-related genes expressed by these cells in fish infected with nervous necrosis virus or immunized with thymus dependent and independent antigens. We found that both CD4 and CD8 T lymphocyte populations significantly increased in these fish and Th1-related genes were up-regulated compared to the control group. Collectively, these findings suggest that the CD4 and CD8 T lymphocytes in olive flounder are similar to the helper and cytotoxic T cells found in mammals, and Th1 and cytotoxic immune responses are primarily involved in the early adaptive immune response against extracellular antigens.
Highlights
In higher vertebrates, the T cells thatplayan essential role in the adaptive immune response are divided into two subsets according to their function, namely helper T cells and cytotoxic T cells [1,2,3]
Based on the analysis of CD8α and CD8β amino acid sequences (Figures 1 and 2), three peptides located in the extracellular domain were selected and the amino residues were synthesized as immunogens for immunizing the mice (Tables 1 and 2)
These results indicate that the monoclonal antibodies (mAbs) developed in the study, detect lymphocytes and the binding sites of the mAbs appear to be on the cell surface
Summary
The T cells thatplayan essential role in the adaptive immune response are divided into two subsets according to their function, namely helper T cells and cytotoxic T cells [1,2,3]. The teleost CD8-like molecule is divided into two distinct genes, CD8α and CD8β, and ismainly expressed on the surface of T cells as a heterodimer consisting of an α-chain and a β-chain [25] Both teleost CD8α and CD8β subunits, similar to mammalian CD8 molecules, are composed of an Ig superfamily (IgSf) domain, a hinge region, a transmembrane domain and a cytoplasmic tail [10,25]. It seems that the overall organization of CD8 genes has been conserved throughout the evolution of vertebrates, with the major regions represented in both mammals and fish. We examined the function of Th1 and Th2 cytokines produced in response to NNV, KLH and LPS stimulation, including the expression of Th-specific cytokines and transcription factors
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