Table 2. Presence of immune cells in cancer.

Macrophages

They adapt their phenotype to the dynamically changing microenvironment that they encounter. TAMs are derived from circulating monocytes or resident tissue macrophages, found within the stroma of many tumor types.

Myeloid-derived suppress cells (MDSCs)

This cells are a heterogeneous type of immune cell, which have a defined immunosuppressive function. Different factors derived from tumor microenvironment allow their expansion, in turn MDSC inhibit immune attack affecting T-cell response by several mechanisms.23

Dendritic cells (DC)

Are essential to induce immunity against cancer. Immature (non-activated) DC can present self-antigens to T cells, which leads to immune tolerance either through T-cell deletion or through the differentiation of regulatory or suppressor T cells. Mature (activated) antigen-loaded DC, can start the differentiation of antigen-specific T cells into effectors T cells. DCs capture tumor antigens released from tumor cells and cross-present them to T cells, contributing to tumor rejection.24

Natural killer cells (NK)

Provide rapid responses to transformed cancer cells. Infiltration of tumors with NK cells has been shown to represent a positive prognostic marker in colorectal,26 gastric27 and lung carcinoma.28

B cells

High numbers of B-lymphocytes have been found in aggregates with other immune cells at the inflammatory site in tumor tissues of various human cancers.29 The intratumoral presence of B cells has been correlated with enhanced survival in patients with ovarian30 and non-small lung cancer.31

T cells

There are several subsets of T cells, within CD4+ (helper) and CD8+ (cytotoxic), that recognize antigens expressed in most tumor cells. Enhanced intratumoral CD8+ T-cell infiltration has been observed to be a positive prognostic marker in melanoma, head and neck, breast, bladder, urothelial, ovarian, colorectal, prostatic and lung cancers.32

Abbreviation: TAM, tumor-associated macrophage.