Table 1.

Immunosuppressive mechanisms employed by MDSCs and TAMs, as well as stereotypic programming that regulate the mechanisms.

	Effect	Tumor type	References
Immunosuppressive mechanism
PD-1/PD-L1	T-cell exhaustion/suppression Myeloid cell suppressive programming	Glioma, Breast, Lung (non-small cell)	(45, 55, 58–61) (108, 109)
CTLA-4/CD80/86	T-cell exhaustion	Breast, Lung	(45, 58, 110, 111)
B7-H3 Receptor/B7-H3	T-cell exhaustion/suppression	Breast, Lung	(206, 207)
ARG	Environmental nutrient depletion	Breast, Lung	(45, 62, 63)
IDO	Environmental nutrient depletion	Breast, Lung	(55)
NOS	T-cell suppression	Breast, Brain, Lung	(12, 23, 45, 55, 62, 68, 69)
ROS	T-cell suppression	Breast, Brain, Lung	(12, 55)
Immunosuppressive program
STAT	Inhibition of intracellular inflammation cascade in suppressive myeloid cells Anti-apoptosis in suppressive myeloid cells	Breast, Brain (GBM), Lung	(75–78, 81, 82) (27, 79, 80)
PPARγ	Inhibition of intracellular inflammation cascade in suppressive myeloid cells Metabolic reprogramming in suppressive myeloid cells	Lung, Breast	(74, 75) (83)