Contrasted TCRβ Diversity of CD8+ and CD8− T Cells in Rainbow Trout

Abstract

Teleost fish express highly diverse naive TCRβ (TRB) repertoires and mount strong public and private clonal responses upon infection with pathogens. Fish T cells express typical markers such as CD8, CD4-1 and CD4-2, CD3, CD28 and CTLA4. Fish CD8+ T cells have been shown to be responsible for antigen-specific cell-mediated cytotoxicity in in vitro systems using histo-compatible effector and target cells. We compare here the complexity of TRB repertoires between FACS sorted CD8+ and CD8− T cells from spleen and pronephros of rainbow trout. In contrast to human, while the TRB repertoire is highly diverse and polyclonal in CD8+ T cells of naïve fish, it appeared very different in CD8− lymphocytes with irregular CDR3 length distributions suggesting a dominance of activated clones already in naïve fish or the presence of non conventional T cells. After infection with a systemic virus, CD8+ T cells mount a typical response with significant skewing of CDR3 length profiles. The infection also induces significant modifications of the TRB repertoire expressed by the CD8− fraction, but for a different set of V/J combinations. In this fraction, the antiviral response results in an increase of the peak diversity of spectratypes. This unusual observation reflects the presence of a number of T cell expansions that rise the relative importance of minor peaks of the highly skewed distributions observed in unchallenged animals. These results suggest that the diversity of TRB expressed by CD8+ and CD8− αβ T cells may be subjected to different regulatory patterns in fish and in mammals.

Kinetics of local and systemic immune cell responses in whirling disease infection and resistance in rainbow trout

“…Within the T cells population, CD8 + T cells were recognized using anti-CD8α MAb. All T cells except CD8 + T cells were defined as CD8 − T cells likely CD4 + T helper cells [25–28].

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Novel Teleost CD4-Bearing Cell Populations Provide Insights into the Evolutionary Origins and Primordial Roles of CD4+ Lymphocytes and CD4+ Macrophages

“…The spectratyping of T-cell receptor beta variable region (TRBV) CDR3 length (Immunoscope analysis) were performed as previously described (37). Primer sequences for the spectratyping of TRBV CDR3 length are shown in Supplemental Table I.…”

“…Primer sequences for the spectratyping of TRBV CDR3 length are shown in Supplemental Table I. The repertoire diversity can be assessed by a diversity score based on the concept of Shannon entropy that provides a measure of the quantity of information encompassed in the repertoire (37, 38). Repertoire diversity scores were used to perform Principal Component Analysis (PCA) in order to compare the statistical dispersion of the samples on a multidimensional plan.…”

Dissecting the immune pathways stimulated following injection vaccination of rainbow trout (Oncorhynchus mykiss) against enteric redmouth disease (ERM)

“…Thus at the mixed tissue level, changes of gene expression in a specific cell type(s) may be diluted by the presence of other abundant cell types or by the changes in other cell types. The possibility to isolate relevant fish leucocyte populations, such as CD4+ or CD8+ cells, and study their responses has become possible in fish recently using antibodies[66][67][68] or transgenic fish[69]. For example in trout infected with Y. ruckeri 4 days earlier, upregulation of Th1 (IL-2, IFN-γ) and Th17 cytokines (IL-17A/F1a, IL-21, IL-22) is apparent in splenic CD4-1+/CD4-2+ cells and CD4-1-/CD4-2+…”