non-structural protein 1 (NS1) An inﬂuenza A virus protein that inhibits TRIM25, an intermediate signaling protein downstream of the viral sensors RIG-I and MDA-5, thereby promoting evasion of innate immunity.
nuclear factor of activated T cells A family of transcription factors that are activated in response to increased cytoplasmic calcium following antigen receptor signaling in lymphocytes.
nucleotide-binding oligomerization domain (NOD) A type of conserved domain originally recognized in ATP-binding cassette (ABC) transporters present present in a large number of proteins, but which also mediates protein homooligomerization.
nude A mutation in mice that results in hairlessness and defective formation of the thymic stroma, so that mice homozygous for this mutation have no mature T cells.
NY-ESO-1 A particular highly immunogenic cancer-testis antigen expressed by many types of human tumors including melanoma.
occupational allergies An allergic reaction induced to an allergen to which someone is habitually exposed in their work.
oligoadenylate synthetase Enzyme produced in response to stimulation of cells by interferon. It synthesizes unusual nucleotide polymers, which in turn activate a ribonuclease that degrades viral RNA.
Omenn syndrome A severe immunodeficiency disease characterized by defects in either of the RAG genes. Affected individuals make small amounts of functional RAG protein, allowing a small amount of V(D)J recombination.
opsonization The coating of the surface of a pathogen by antibody and/or complement that makes it more easily ingested by phagocytes.
oral tolerance The suppression of specific systemic immune responses to an antigen by the prior administration of the same antigen by the oral (enteric) route.
original antigenic sin The tendency of humans to make antibody responses to those epitopes shared between the first strain of a virus they encounter and subsequent related viruses, while ignoring other highly immunogenic epitopes on the second and subsequent viruses.
p50 See NFκB.
p65 See NFκB.
PA28 proteasome-activator complex A multisubunit protein complex induced by interferon-γ that takes the place of the 19S regulatory cap of the proteasome and increases the rate of peptides exiting from the proteasome catalytic core.
palatine tonsils Paired masses of organized peripheral lymphoid tissues located on each side of the throat, and in which an adaptive immune response can be generated. They are part of the mucosal immune system.
Paneth cells   Specialized epithelial cells at the base of the crypts in the small intestine that secrete antimicrobial peptides.
papain A protease that cleaves the IgG antibody molecule on the amino-terminal side of disulfide linkages, producing two Fab fragments and one Fc fragment.
paracortical areas The T-cell area of lymph nodes.
paracrine Describes a cytokine or other biologically active molecule acting on cells near to those that produce it.
parasites   Organisms that obtain sustenance from a live host. In immunology, it refers to worms and protozoa, the subject matter of parasitology.
paroxysmal nocturnal hemoglobinuria A disease in which complement regulatory proteins are defective, so that activation of complement binding to red blood cells leads to episodes of spontaneous hemolysis.
passive immunization The injection of antibody or immune serum into a naive recipient to provide specific immunological protection. Cf. active immunization.
pathogen Microorganism that typically causes disease when it infects a host.
pathogen-associated molecular patterns (PAMPs) Molecules specifically associated with groups of pathogens that are recognized by cells of the innate immune system.
pathogenesis The origin or cause of the pathology of a disease.
pathogenic microorganisms Microorganism that typically causes disease when it infects a host.