Figure 1.

Th1 immune evasion induced by HPV in tumor microenvironment. HPV (1) interferes in TLR expression and in immune signalling pathways; (2) suppresses IL-12 expression, leading to a decreased production of IFNs (type I and IFN-γ) and blocking macrophages (M1 phenotype) and dendritic cell (DC) activity; (3) promotes downregulation of HLA expression and transportation to membrane surface, preventing antigen presentation, T cell activation, and NK and CTL cytotoxicity; and (4) finally, the downregulation of lymphocyte activity related to a decreased activity of APC cells (as M1 and DC) impairs adaptive immune activation [2].