Immune Reactions against Tumors

Immune Reactions against Tumors

Tumor antigens are capable of eliciting a comprehensive immune response involving both the cellular and humoral immune responses.

◗ Cellular immune responses

T lymphocytes play an important role in tumor immunity. They act both as cytotoxic effector cells and as central modulating cells. Through these effector cells, they control the specific cell-mediated antitumor immune responses and upregulate non-specific killing mechanisms. The activation of T lymphocytes by tumor cell products as a consequence of antigen recognition may result in the secretion of nonspecific immunoregulatory factors.

·           These factors are capable of “upregulating” the tumor-killing function of mononuclear phagocytes, NK cells, and granulocytes.

·           These factors also enhance the ability of NK cells and mono-cytes to participate in ADCC against tumor cells.

·           Macrophages also play an important role in tumor response. Clustering of macrophages around tumor cells is associated with tumor regression and seen in the case of numerous cancers.

◗ Humoral immune responses

B lymphocytes produce tumor-specific antibodies, which may induce complement-dependent cytotoxicity of tumor cells or may mediate ADCC. ADCC can be mediated by a variety of cells expressing Fc receptors (NK cells, monocytes or macrophages, and granulocytes) by recognizing and destroying IgG-coated tumor cells.