cyclic neutropenia A dominantly inherited disease in which neutrophil numbers ﬂuctuate from near normal to very low or absent, with an approximate cycle time of 21 days. This is in contrast to severe congenital neutropenia (SCN), in which the inherited defect results in persistently low neutrophil numbers.
cyclic reentry model An explanation of the behavior of B cells in lymphoid follicles, proposing that activated B cells in germinal centers lose and gain expression of the chemokine receptor CXCR4 and thus move from the light zone to the dark zone and back again under the inﬂuence of the chemokine CXCL12.
cyclophilins A family of prolylisomerases that affect protein folding, that also bind cyclosporin A to produce a complex that associates with calcineurin, preventing its activation by calmodulin.
cyclophosphamide A DNA alkylating agent that is used as an immunosuppressive drug. It acts by killing rapidly dividing cells, including lymphocytes proliferating in response to antigen.
cyclosporin A (CsA) A powerful noncytotoxic immunosuppressive drug that inhibits signaling from the T-cell receptor, preventing T-cell activation and effector function. It binds to cyclophilin, and the complex formed binds to and inactivates the phosphatase calcineurin.
cystic fibrosis Disease caused by defect in CFTR gene, leading to abnormally thick mucus and causing serious recurrent infections of the lung.
cytidine deaminase activity (CDA) An enzymatic activity exhibited by AID-APOBEC family proteins of agnathan species that may mediate rearrangement and assembly of complete VLR genes.
cytokines Proteins made by a cell that affect the behavior of other cells, particularly immune cells. Cytokines made by lymphocytes are often called interleukins (abbreviated IL). Cytokines and their receptors are listed in Appendix III. Cf. chemokines.
cytomegalovirus UL16 protein A nonessential glycoprotein of cytomegalovirus that is recognized by innate receptors expressed by NK cells.
cytosol One of several major compartments within cells containing elements such as the cytoskeleton, and mitochondria, and separated by membranes from distinct compartments such as the nucleus and vesicular system.
cytotoxic T cells T cells that can kill other cells, typically CD8 T cells defending against intracellular pathogens that live or reproduce in the cytosol, but in some cases also CD4 T cells.
daclizumab Antibody to human CD25 used to block IL-2 receptor signaling in T cells for treatment of rejection in renal transplantation.
DAG See diacylglycerol.
damage-associated molecular patterns (DAMPs) See pathogen-associated molecular patterns (PAMPs).
DAP10, DAP12   Signaling chains containing ITAMS that are associated with the tails of some activating receptors on NK cells.
dark zone See germinal center.
DC-SIGN A lectin on the dendritic-cell surface that binds ICAM-3 with high affinity.
DDX41 (DEAD box polypeptide 41) A candidate DNA sensor of the RLR family that appears to signal through the STING pathway.
death effector domain (DED) Protein-interaction domain originally discovered in proteins involved in programmed cell death or apoptosis. As part of the intracellular domains of some adaptor proteins, death domains are involved in transmitting pro-inﬂammatory and/or pro-apoptotic signals.
death-inducing signaling complex (DISC) A multi-protein complex that is formed by signaling through members of the ‘death receptor’ family of apoptosis-inducing cellular receptors, such as Fas. It activates the caspase cascade to induce apoptosis.