In a tumor sample, if tumor cells express PD-L1 but there is no expression of PD1 in the same sample, is there another receptor for PD-L1 that might mediate suppression of T cells? What is the reason for expression of PD-L1 in the absence of PD-1? Or will tumor cells just aberrantly express PD-L1 even if it serves no purpose?
Hello Leandro Bomans
Is there another receptor for PD-L1 that might mediate suppression of T cells ?
As far as I know I don't think there is another receptor for PD-L1.
Based on the presence or absence of T cells and the expression of PD-L1 by cancer cells, a tumor can be categorized into four groups:
(1) PD-L1 positive, T cell positive
(2) PD-L1 negative, T cell positive
(3) PD-L1 positive, T cell negative and
(4) PD-L1 negative, T cell negative
A tumor can be positive or negative for surface PD-L1 expression through several biological processes, thereby having different clinical significance. These can be categorized as follows:
(a) genetic mechanisms that lead to constitutive PD-L1 expression,
(b) induced PD-L1 expression by the presence of T cells,
(c) absence of T cells leading to no reactive PD-L1 expression, and
(d) genetic events that preclude PD-L1 expression upon T cell infiltration.
It is conceivable that the presence or absence of cancer cell surface PD-L1 may have different functional meaning depending on the underlying mechanism of expression.
Best.
Dear Leonardo, the targeted receptor for the PD-L1 usually located on the immune cells. Tumor and other somatic cells secret PD-L1 not for another tumor cells/somatic cells, but for the immune cells, to prevente immune attac. This secretion isn't depended of presence of immune cells in culture. So, if you have no immune cells in the culture secretion of PD-L1 by tumor cells continuing despite absence of the PD.
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