dislocation   In reference to viral defense mechanisms, the degradation of newly synthesized MHC class I molecules by viral proteins.
disseminated intravascular coagulation (DIC) Blood clotting occurring simultaneously in small vessels throughout the body in response to disseminated TNF-α, which leads to the massive consumption of clotting proteins, so that the patient’s blood cannot clot appropriately. Seen in septic shock.
diversion colitis   Inﬂammation and necrosis of intestinal enterocytes following surgical diversion of normal ﬂow of fecal contents due to impaired metabolism resulting from loss of short-chain fatty acids derived from microbiota.
diversity gene segment (DH) Short DNA sequences that form a join between the V and J gene segments in rearranged immunoglobulin heavy-chain genes and in T-cell receptor βand δ-chain genes. See gene segments.
DN1, DN2, DN3, DN4 Substages in the development of CD4+CD8+ double-positive T cells in the thymus. Rearrangement of the TCRβ-chain locus starts at DN2 and is completed by DN4.
DNA-dependent protein kinase (DNA-PK) Protein kinase in the DNA repair pathway involved in the rearrangement of immunoglobulin and T-cell receptor genes.
DNA ligase IV Enzyme responsible for joining the DNA ends to produce the coding joint during V(D)J recombination.
DNA transposons Genetic elements encoding their own transposase that can insert themselves into and excise themselves from the DNA genomes of a host.
DNA vaccination Vaccination by introduction into skin and muscle of DNA encoding the desired antigen; the expressed protein can then elicit antibody and T-cell responses.
donor lymphocyte infusion (DLI) Transfer of mature lymphocytes (i.e., T cells) from donor into patients during bone marrow transplantation for cancer treatment to help eliminate residual tumor.
double-negative thymocytes   Immature T cells in the thymus that lack expression of the two co-receptors CD4 and CD8 and represent the progenitors to the remaining T cells developing in the thymus. In a normal thymus, these represent about 5% of thymocytes.
double-positive thymocytes   Immature T cells in the thymus that are characterized by expression of both the CD4 and the CD8 co-receptor proteins. They represent the majority (about 80%) of thymocytes and are the progenitors to the mature CD4 and CD8 T cells.
double-strand break repair (DSBR) A nonhomologous end joining pathway of DNA repair used in the completion of isotype switching.
double-stranded RNA (dsRNA) A chemical structure that is a replicative intermediate of many viruses that is recognized by TLR-3.
Down syndrome cell adhesion molecule (Dscam) See Dscam.
DR4, DR5   Members of the TNFR superfamily expressed by many cell types that can be activated by the TRAIL to induce apoptosis.
draining lymph nodes A lymph node downstream of a site of infection that receives antigens and microbes from the site via the lymphatic system. Draining lymph nodes often enlarge enormously during an immune response and can be palpated; they were originally called swollen glands.
Dscam A member of the immunoglobulin superfamily that in insects is thought to opsonize invading bacteria and aid their engulfment by phagocytes. It can be made in a multiplicity of different forms as a result of alternative splicing.
dysbiosis Altered balance of microbial species comprising the microbiota resulting from a variety of causes (e.g., antibiotics, genetic disorders) and frequently associated with outgrowth of pathogenic organisms such as Clostridium difficile.
dysregulated self Refers to changes that take place in infected or malignant cells that alter expression of various surface receptors that can be detected by the innate immune system.