Table 2.

Tumor-associated immune cells within the TME and their related functions

Functions	Cell types	Role in tumor angiogenesis
Tumor-suppressing immune cells	Effector T cells	Killing of cancer cells by granule exocytosis and FasL-mediated apoptosis induction Polarizing M2-TAMs to M1-TAMs and induce DC maturation
	Effector B cells	Production of TH1 cytokines, enhanced CTL activity, and NK cell-meditated tumor cell killing
	Natural killer cells (NK cells)	Production of pro-inflammatory cytokines and chemokines, release of granules containing perforin and granzymes that induce the apoptosis of tumor cells
	Dendritic cells (DCs)	Processing and presentation tumor antigens to naïve T cells Production of IL-12 and IL-18 to induce the activation and proliferation of Treg cells
	M1-tumor-associated macrophages (TAMs)	Promotion tumor elimination through secretion of pro-inflammatory cytokines and generation of high levels of reactive oxygen/nitrogen species Induction vessel maturation by secreting anti-angiogenic cytokines
Tumor-promoting immune cells	M2-tumor-associated macrophages (TAMs)	Promotion of tumor escape by inducing anti-inflammatory TH2 responses through secretion of IL-10 and TGF-β
	Regulatory T cells (Treg cells)	Secreting cytokines such as IL-10, TGF-β; establishing an immunosuppressive environment; associated with poor prognosis
	Myeloid-derived suppressor cells (MDSCs)	Inhibition of T cell function by production of iNOS from arginine and immunosuppressive cytokines Associated with tumor progression and neo-angiogenesis; suppressing T cells and NK cells; differentiating into TAMs under hypoxic conditions
	Regulatory B cells (Breg cells)	Production of IL-10 and IL-35 to inhibit effector T cell function and promote an immunosuppressive environment