33.3.1 Innate immune response to tumors

Natural killer cells (NK cells)

Around 15% of mammalian blood lymphocytes are composed of NK cells. NK cells can be activated by interferons from virus infected cells or by IL-12 from activated macrophages. NK cells are large, granular, and non-phagocytic cells that are derived from bone marrow. NK cells can kill certain tumor cell lines and are quite effective in eliminating the cells that diminish class I MHC expression. Studies also indicate that patients with deficiency of NK cells are more likely to suffer from EBV- associated lymphomas. NK cells express CD56 and CD16 antigen receptors over their surface. Activation of NK cells by antigen antibody reaction through CD16 kills the target cells.

Macrophages

Macrophages can prevent the spread of cancer based on their activation state. Activated macrophages can kill transformed cells more efficiently than the normal cell.M1 cells especially treat the tumor cells like an infectious organism and produces cytokine tumor necrosis factor (TNF) to kill the tumor but M2 macrophages on the other hand are associated with tumor progression.

33.3.2 Adaptive immune response to tumors

T-lymphocytes

The basis of adaptive tumor immunity is to destroy tumor cells by CD8+ CTLs. Functioning of CD8+ cell requires cross presentation of the tumor antigen by the dendritic cells. Although CD8+ CTLs have a substantial role to play in killing the transformed clones but not much is known about the efficacy of CD4+ helper T –cells in tumor immunity.