Table 1.

Summary of some of the common regulatory mediators in HR-HPV- induced malignancies.

Immunoregulatory factors	Main source	Mechanisms of immune regulation	Possible effect	Reference
Arg-1	DCs and other myeloid cells	•Depletion of arginine	•Inhibit T cells proliferation and function	[88]
TGF-β & IL-10	Tumor cells, TAM, Treg cells, DCs	•Modulate DC maturation •↓Overall immune activation	•$\uparrow$Treg cell and regulatory DC differentiation •↓Lymphocyte functions	[91], [93], [94], [95], [96]
IFN-γ	Activated T cells	•↑IDO and PD-L production	•↑Treg function •↓T cell effector function	[88], [89], [95]
PD-L1	Tumor cells, APCs	•Delivers inhibitory signal to T cells via PD1 receptor molecules	•↓T cell activation and proliferation	[75], [93], [130]
PD-1	T cells	•Delivers intracellular negative signal	•Induce T cell anergy or exhaustion	[93], [132]
CTLA-4	T cells	•Competitively inhibit CD80 and CD86 co-stimulatory functions •Induce IDO production	•↓T cell effector function	[107], [108], [110]
IDO-1	Tumor cells, DCs	•Depletion of tryptophan •↑ toxic tryptophan metabolites	•↑T cell apoptosis •↓T cell effector function	[88], [89], [122], [123], [124]