Immune Suppression Markers
Within the tumour microenvironment, tumour cells and proteins can act through multiple pathways to suppress T-cell activation, trigger T-cell exhaustion, or activate regulatory T cells (Tregs).
Lymphocyte-activation gene 3 (LAG-3) is an immune checkpoint receptor protein expressed on the cell surface of activated cytotoxic t cells and regulatory T cells. Increased expression of LAG-3 can promote T-cell exhaustion and also suppress the functioning of cytotoxic T-cells through Tregs.
Regulatory T cells (Tregs) are suppressor T cells that modulate immune response by keeping a check on the activation of cytotoxic T cells. Increased infiltration of Tregs into the tumour microenvironment has been found in several types of tumour.
Myeloid-derived suppressor cells (MDSCs) are immature heterogeneous immune cells belonging to myeloid lineage. The population of MDSCs expand during cancer, infections, chronic inflammation, and traumatic stress to regulate immune response. They are found in different tumours types and their microenvironments and help in suppressing cytotoxic T cell function.
Indoleamine 2, 3-dioxygenase-1 (IDO1) is a heme-containing enzyme that is involved in tryptophan metabolism. It promotes the breakdown of tryptophan into immunosuppressive kynurenine in the tumour microenvironment. It is expressed in response to inflammation and supresses the T cell activity. It may be expressed by different cells, including tumour cells.