Immunology is one of the oldest biomedical disciplines, and it involves the entire body. As such, one of the challenges for students and investigators who do not have a background in immunology is the immunological terms and their definitions. The Cancer Immunology Essentials Glossary includes relevant terms from the Cancer Immunology Research's Masters of Immunology and Cancer Immunology at the Crossroads primers with definitions provided by the authors. The Glossary will be updated with relevant terms from each Masters primer, and the definitions will be refined with advances in the field.

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Adaptive immunity

Precise host immune response mounted by lymphocytes against targets after antigen presentation.



Additives to enhance effectiveness of vaccines. Many adjuvants mimic bacterial or viral structures and interact with one of the families of host Pattern Recognition Receptors and serve as a "danger" signal to the host. Other adjuvants serve to initiate a local inflammatory response. Common vaccine adjuvants include chemical or oil emulsions, RNA or DNA oligonucleotides, and small molecules with a variety of chemical structures.


Antigen processing and presentation

Conversion of proteins into peptide–MHC complexes prior to recognition and engagement by T cells.



Control trafficking patterns of leukocytes with specific adhesion receptors by chemokine gradients leading to or from the appropriate lymphoid organs.


Central tolerance

The component of immune tolerance that occurs during early T-cell development. Central tolerance serves as the step wherein T cells reactive to most self-antigens (auto-reactive T cells) are removed from the T-cell repertoire in the thymus and therefore never appear in the circulation.



The process in professional APCs of internalization of extracellular antigens and transfer into the cytoplasm for proteasomal processing and binding to MHC class I for presentation to CD8 T cells.


Cytotoxic T cell (CTL)

Expresses the CD8 glycoprotein markers and interacts with Class I MHC products on target cells.


Dendritic cells (DC)

The most important professional antigen presenting cells (APC) capable of expressing all molecules required to initiate an adaptive immune response.



Part of the antigen recognized by the immune system.



Monoclonal antibody directed against the epidermal growth factor receptor and used in clinical treatment of colorectal and head and neck cancers.


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Human Leukocyte Antigens (HLA)

A family of genes encoding cell-surface glycoproteins with thousands of polymorphic variants each representing a distinct HLA product. There are two classes of HLA, I and II, which bind and present peptides to the TCR. All nucleated cells can synthesize Class I HLA. Class II HLA molecules are expressed on all professional APCs, which engage T cells expressing the CD4 glycoprotein markers. In mice, these glycoproteins are called Major Histocompatibility Complex (MHC).



Immune exhaustion

Characterized by the expression of the PD-1 marker on T cells resulting from persistent activation of antigen-specific T cells, as in chronic infections and autoimmunity, and in response to certain cancers.


Immune surveillance

Host immune defense mechanisms comprising innate and adaptive immunity.


Immune tolerance

A condition of normal host immune defense established during early lymphocyte development in the absence of foreign (non-self) antigens, and based on the recognition of self antigens. A state of self-tolerance poses a hurdle for immune recognition of malignantly transformed cells.



The hypothesis that host immunity against a cancer can result in an evolutionary adaption in the tumor resulting in reduced immunogenicity and/or escape from existing immune pressure. This adaption is most commonly due to loss or decreased expression of immunogenic epitopes.



Antigen receptors on B-lymphocytes comprising heterodimers of a light and a heavy chain held together by disulfide bonds.


Innate immunity

Hard-wired host defense mechanisms capable of immediate response to targets to maintain homeostasis. Innate immunity comprises macrophages, neutrophils, mast cells, natural killer (NK) cells, dendritic cells (DC), and the complement cascade.



Intracellular compartments rich in proteases for breaking down proteins that enter the cell via endocytosis or are in specialized cells via phagocytosis.


Major histocompatibility complex (MHC)

A family of genes encoding cell-surface glycoproteins with thousands of polymorphic variants each representing a distinct MHC product. There are two classes of MHC, I and II, which bind and present peptides to the TCR. All nucleated cells can synthesize Class I MHC. Class II MHC molecules are expressed on all professional APCs, which engage T cells expressing the CD4 glycoprotein markers. In humans, these glycoproteins are called Human Leukocyte Antigens (HLA).

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Natural killer (NK) cells

Bone marrow–derived cells with receptors that recognize MHC Class I products. NK cells can diagnose and kill target cells lacking self-MHC products; they can produce cytokines that activate macrophages and contribute to the inflammatory tumor microenvironment (TME) .



A class of antigens derived from mutated proteins that are present only in tumor cells or from viral proteins in virally-infected cells.


Neutralizing antibodies

Antibodies with specificity for incoming viruses that can bind and eliminate viruses before they have a chance to gain a foothold in the host.


Oncogenic driver

Genetic mutation that initiates oncogenesis and is often required for tumor cell survival.



Peripheral tolerance

The component of immune tolerance in which any mature T cells that have exited the thymus and have the capability to recognize self-antigens are suppressed by regulatory mechanisms.



The key protease in the cytosol responsible for generation of peptides, which are assembled together with the Class I MHC subunits in the endoplasmic reticulum.


Regulatory cells

Myeloid-derived suppressor cells (MDSC) and regulatory lymphocytes (Breg; Treg) maintain immune homeostasis by inducing immune tolerance to avoid damaging self-reactive responses or by activating immune functions against damaging targets.



Monoclonal antibody directed against the CD20 marker on B cells and used in clinical treatment of B-cell malignancies.


T-cell costimulatory molecules

Sets of cell surface proteins whose interactions regulate T-cell activation. Receptors identified to date include CTLA-4 and PD-1 on T cells and their ligands B7-1 (CD80), B7-2 (CD86), PD-L1 (B7-H1), and PD-L2 (B7-DC) on antigen-presenting or target cells.


T-cell receptor (TCR)

Antigen receptor on T-lymphocyte comprising similar heterodimer as immunoglobulin but uses a different mode of antigen recognition by binding to the peptide-loaded products of the MHC.

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Updated: 12 September 2014  11:00 am EST