viral integrase inhibitors Drugs that inhibit the action of the HIV integrase, so that the virus cannot integrate into the host-cell genome.
viral protease Enzyme encoded by the human immunodeficiency virus that cleaves the long polyprotein products of the viral genes into individual proteins.
viral set point   In human immunodeficiency virus infection, the level of HIV virions persisting in the blood after the acute phase of infection has passed.
virus Pathogen composed of a nucleic acid genome enclosed in a protein coat. Viruses can replicate only in a living cell, because they do not possess the metabolic machinery for independent life.
virus-neutralizing antibodies Antibodies that block the ability of a virus to establish infection of cells.
vitronectin See S-protein.
VLRs See variable lymphocyte receptors.
VpreB See surrogate light chain.
WAS See Wiskott–Aldrich syndrome.
WASp The protein defective in patients with Wiskott–Aldrich syndrome. When activated, WASp promotes actin polymerization.
Weibel–Palade bodies Granules within endothelial cells that contain P-selectin.
wheal-and-flare reaction A skin reaction observed in an allergic individual when an allergen to which the individual has been sensitized is injected into the dermis. It consists of a raised area of skin containing edema ﬂuid, and a spreading, red, itchy inﬂammatory reaction around it.
white pulp The discrete areas of lymphoid tissue in the spleen.
Wiskott–Aldrich syndrome (WAS) An immunodeficiency disease characterized by defects in the cytoskeleton of cells due to a mutation in the protein WASp, which is involved in interactions with the actin cytoskeleton. Patients with this disease are highly susceptible to infections with pyogenic bacteria due to defects in T-follicular helper cell interactions with B cells.
XBP1 (X-box binding protein 1) A transcription factor that induces genes required for optimal protein secretion by plasma cells, and is part of the unfolded protein response. XBP1 mRNA is spliced from an inactive to an active form by signals produced by ER stress.
XCR1 A chemokine receptor selectively expressed by a subset of dendritic cells that are specialized for cross-presentation whose development requires the transcription factor BATF3.
xenografts Grafted organs taken from a different species than the recipient.
xenoimmunity   In the context of immune-mediated disease, refers to immunity directed against foreign antigens of non-human species, such as bacteria-derived antigens of the commensal microbiota that are targets in inﬂammatory bowel disease (IBD).
xeroderma pigmentosum Several autosomal recessive diseases caused by defects in repair of ultraviolet light-induced DNA damage. Defects in Polη cause type V xeroderma pigmentosum.
xid See X-linked immunodeficiency.
X-linked agammaglobulinemia (XLA) A genetic disorder in which B-cell development is arrested at the pre-B-cell stage and no mature B cells or antibodies are formed. The disease is due to a defect in the gene encoding the protein tyrosine kinase Btk, which is encoded on the X chromosome.
X-linked hyper IgM syndrome See CD40 ligand deficiency.
A syndrome with some features resembling hyper IgM syndrome. It is caused by mutations in the protein NEMO, a component of the NFκB signaling pathway. Also called NEMO deficiency.
X-linked immunodeficiency An immunodeficiency disease in mice due to defects in the protein tyrosine kinase Btk. Shares the gene defect with X-linked agammaglobulinemia in humans, but leads to a milder B cell defect than seen in the human disease.