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Immunological Vocabulary for Beginners


Allogeneic: A term describing non-self cells or tissues that differ from the host cells at the MHC locus or at other loci (Janeway et al., 2005).


Allograft: A tissue graft from an allogeneic donor. Allografts are rejected by the immune system unless the recipient of the graft undergoes immunosuppressant therapy (Janewayet al., 2005).


B cell: A B cell functions both as an antigen-presenting cell and as an effector cell in the humoral immune response. Once activated, it produces and releases antibodies (Janeway et al., 2005).


CD: The CD designation indicates that the molecule so named is a cell-surface molecule that is recognized by a group of monoclonal antibodies known as a cluster of differentiation (Janeway et al., 2005).


Graft-versus-host disease (GVHD): A major complication of allogeneic bone marrow transplantation. In this condition, mature donor T cells from the transplanted bone marrow recognize the recipient’s cells as non-self, leading to a severe inflammatory reaction characterized by rashes, diarrhea, and liver disease (Janeway et al., 2005).


Heterodimer: A functional protein composed of two different polypeptide subchains.


Homodimer: A functional protein composed of two identical polypeptide subchains.


Hypereosinophilia: A condition marked by an abnormally large number of eosinophils circulating in the bloodstream.


Immunoglobulin superfamily: Proteins belonging to this family are involved in antigen recognition and in cell-cell interaction and share structural features with immunoglobulin molecules. Each protein in this family contains one or more immunoglobulin or immunoglobulin-like domains (Janeway, et al., 2005).


Immunosuppressive drug: A compound that inhibits an adaptive immune response. Used mostly to prevent graft rejection and to treat severe autoimmune diseases (Janeway et al., 2005).


Immunotoxin: An anti-self antibody coupled to a toxin usually derived from a plant or an infectious agent. Much immunological research focuses on potential uses of immunotoxins as immunosuppressive drugs (Janeway et al., 2005).


Invariant: Unlike the TCR subchains, which express regions of variable amino acid sequences at their binding sites, all (non-mutated) CD3 subchains of a given type express the exact same amino acid sequence (Janeway et al., 2005).


ITAM: An immunoreceptor tyrosine-based activation motif (ITAM) consists of two tyrosine residues separated by between nine and 12 amino acid residues. In the classic ITAM sequence, either a leucine residue or an isoleucine residue occupies the fourth spot. ITAMs were initially identified in the cytoplasmic tails of CD3 molecules (Janeway et al., 2005).


Missense mutation: A mutation in which one nucleotide base is substituted for another.


Peripheral lymphoid organs: Organs in which immune responses are induced. Include the lymph nodes, the spleen, and mucosal-associated lymphoid tissues (Janeway et al., 2005).


Recombination signal sequence (RSS): A short segment of DNA flanking a gene segment to be rearranged during V(D)J recombination (Janeway et al., 2005).


Severe combined immunodeficiency: An immunodeficiency disease in which the immune system mounts neither T-cell mediated nor humoral responses. Fatal if untreated. Usually results from T cell deficiencies (Janeway et al., 2005).


Src-family tyrosine kinase: A receptor-associated protein tyrosine kinase with an SH2 domain that binds to ITAMs. These enzymes phosphorylate specific ITAMs on the cytoplasmic tails of receptor-associated accessory proteins to initiate a signaling transduction cascade (Janeway et al., 2005).


Thymocyte: A developing T cells found in the thymus. The CD3 complex plays a role in its development (Janeway et al., 2005).


Thymus: A central lymphoid organ in which T cells develop. Located behind the breastbone in the upper chest (Janeway et al., 2005).


T cell: A T cell is an effector cell that function in the cell-mediated immune response. There are three subsets of T cells (TH1, TH2, and cytotoxic) with different effector functions, but all three subsets express the CD3 complex (Janeway et al., 2005).


T-cell antigen receptor (TCR): The receptor on the T-cell surface that recognizes an antigen in the context of an MHC molecule. When TCR is associated with the other proteins in the TCR complex, the binding of a TCR to its peptide:MHC ligand triggers the signaling cascade that activates the T cell (Janeway et al., 2005).


V(D)J recombination: A process found exclusively in lymphocytes that allows for the recombination of gene segments into novel groupings. Accounts for the diversity of TCRs in normal individuals (Janeway et al., 2005).




Literature Cited

Janeway, C. A., Travers, P., Walport, M., Sclomchik, M. J. 2005. Immunobiology: the immune system in health and disease, 6th ed. Garland Science Publishing, NY, pp. 753-777.





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