Immunosuppressive Tumor Microenvironment IHC

The immune system has the capability to detect and eliminate tumor cells, most notably through cytotoxic CD8+ T cell recognition of tumor antigens presented on the surface of tumor cells by MHC class I molecules. However, anti-tumor immune cells can be subject to various immunosuppressive mechanisms in the tumor microenvironment (TME). One of these mechanisms is the upregulation of PD-L1 by tumor cells and myeloid cells, which suppresses T cell function through interaction with PD-1. In addition, the tumor can recruit immunosuppressive cells, such as FoxP3+ regulatory T cells, and can promote polarization of cells to a pro-tumor and immunosuppressive phenotype, such as CD68+CD206+M2-like macrophages. The infiltration and function of cytotoxic CD8+ T cells can also be suppressed by stromal cells such as LRRC15+ immunosuppressive cancer-associated fibroblasts (CAFs).