When I gate singlets, lymphocytes, CD3 and then CD8 in my cytometry analysis, I see that CD8+ lymphocytes are divided in two. One population is very bright, and the other is less bright although it is clearly positive. Are both populations CD8+ T cells?
Dear Dr. Enrique Espinosa,
Also in my experience, CD8 expression levels in CD3+CD8+ cells tend to be more variable than CD4 expression levels in CD3+CD4+ cells. I am not sure of the CD8(dim) evens you encountered, I would cite the below article that summarizes past observations as well as the authors' finding regarding CD8(dim) T cells.
Article Detuning CD8 T cells: Down-regulation of CD8 expression, tet...
- CD8 expression can be inhibited by certain cytokines, including IL-2, -4, and -15, on activated T cells.
- Down-regulation of CD8 has been suggested as one of the mechanisms for peripheral tolerance.
- CD8 low subpopulations have been reported during chronic diseases.
- CD8 down-regulation also occurs during acute immune responses to pathogens.
- CD8 effector T cell differentiation involves a transient down-regulation of antigen sensitivity (CTL “detuning”), via reduced CD8 expression.
And if you include NK1.1 in your panel and exclude NKT cells, do you still have this two subpoulations of CD8+T cells? NKT cells also express CD8 at a different intensity that CD3 T cells.
In line with Daniel´s answer, TCR gamma-delta have a DN (CD4-CD8-) phenotype when they are circulating cells. However, they could display expression of CD8 when these cells are in peripheral tissues, like mucoses.
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