Isolation and Characterization of Salmonid CD4+ T Cells

Abstract

This study reports the isolation and functional characterization of rainbow trout (Oncorhynchus mykiss) CD4-1+ T cells and the establishment of an IL-15–dependent CD4-1+ T cell line. By using Abs specific for CD4-1 and CD3ε it was possible to isolate the double-positive T cells in spleen and head kidney. The morphology and the presence of transcripts for T cell markers in the sorted CD4-1+CD3ε+ cells were studied next. Cells were found to express TCRα, TCRβ, CD152 (CTLA-4), CD154 (CD40L), T-bet, GATA-3, and STAT-1. The sorted CD4-1+ T cells also had a distinctive functional attribute of mammalian T lymphocytes, namely they could undergo Ag-specific proliferation, using OVA as a model Ag. The OVA-stimulated cells showed increased expression of several cytokines, including IFN-γ1, IL-4/13A, IL-15, IL-17D, IL-10, and TGF-β1, perhaps indicating that T cell proliferation led to differentiation into distinct effector phenotypes. Using IL-15 as a growth factor, we have selected a lymphoid cell line derived from rainbow trout head kidney cells. The morphology, cell surface expression of CD4-1, and the presence of transcripts of T cell cytokines and transcription factors indicated that this is a CD4-1+ T cell line. To our knowledge, this is the first demonstration of the presence of CD4-1+CD3ε+ T cells in salmonids. As in mammals, CD4-1+ T cells may be the master regulators of immune responses in fish, and therefore these findings and the new model T cell line developed will contribute to a greater understanding of T cell function and immune responses in teleost fish.

Imaging Flow Cytometry Protocols for Examining Phagocytosis of Microplastics and Bioparticles by Immune Cells of Aquatic Animals

“…The sorted salmon IgM + cells were located in the low BF area and low SSC intensity gate, confirming a close area match to that of the lymphocyte-like cells. Similarly, a previous study on trout HK confirmed lymphocyte localization (low FSC and low SSC) using conventional FC, based on CD4 + T cell markers (26). In addition, employing conventional FC, percentage of IgM + and IgT + B cells in salmon HK cells were determined by gating the same area (25).…”

Rainbow Trout IgM+ B Cells Preferentially Respond to Thymus-Independent Antigens but Are Activated by CD40L

“…Rainbow trout contain two different sequences in their genome that seem to correspond to CD40L homologs, sharing an 81.44% amino acid identity ( Figure S3). Based on these results, in the current study, we focused on determining the levels of expression and the effects of one of these CD40L which was previously reported to be highly expressed in rainbow trout CD4 + T helper cells (37). Before determining the effect of CD40L on rainbow trout IgM + B cells, we verified which leukocyte subsets were expressing this CD40L in this species.…”

Dietary Buglossoides arvensis Oil as a Potential Candidate to Substitute Fish Oil in Rainbow Trout Diets

“…Interleukin‐10 is secreted inter alia by CD4 + T cells (Ng et al, ). These types of cells can also be found in the spleen of rainbow trout (Maisey et al, ). It remains unclear whether the immune‐modulating characteristics of the Ahiflower oil or the increased PUFA levels in the A66 and A100 diets per se might have affected the constitution of the spleen.…”