Glossary of terms Flashcards
Adaptive immunity
Immune responses mediated by lymphocytes and their products requiring activation by innate immune mechanisms on first encounter with antigen but acting immediately on subsequent encounters
Afferent lymphocytes
lymphatic vessels entering lymph nodes from tissue spaces
Affinity
The strength of a noncovalent binding reaction; the higher the affinity, the more likely two partners will exist in a complex
Alveolar macrophages
Macrophages in the lung
Antibodies
Highly variable proteins produced by B lymphocytes of the immune system and that recognise the antigen and target it for destruction
Antibody-dependent cellular cytotoxicity (ADCC)
A process whereby FcR-bearing cells encounter an antibody-coated target cell and degranulate, releasing contents that kill the antibody-coated cell
Antigen
Any molecule or part of a molecule recognised by the variable antigen receptor of the lymphocytes
Antigenic-drift (of influenza virus)
Point mutations, predominantly in hemagglutinin and neuraminidase, that affect recognition by neutralizing human antibodies. Antigenic drift gives rise to pandemic outbreaks
Hemagglutination
Refers to glycoproteins which cause red blood cells to agglutinate. This process is called hemagglutination. Antibodies and lectins are commonly known hemagglutinins
Neuraminidase enzymes
Glycoside hydrolase enzymes that cleave the glycosidic linkages of neuraminic acids.
Antigenic-shift (of influenza virus)
The reassortment of independent RNA segments from two different influenza genomes to generate a recombinant virus with new antigenic subtypes. Antigenic-shift gives rise to pandemic outbreaks
Antigenic variation (in parasites)
Clonal expression of members of proteins among parasite progeny; examples include the major surface glycoproteins of trypanosomes and the red cell adhesins encoded by malaria parasites; variant expression allows parasites to evade immune recognition
Antigen presentation
The binding of fragments of intracellular molecules, usually peptides derived from proteins of pathogens, by major histocompatibility complex (MHC) molecules and their presentation on the cell surface for recognition by T cells
Antigen presenting cells
Cells that are capable of presenting an antigen for recognition by T cells and of activating naive T cells
Antimicrobial peptides
Peptide antibodies that provide defense against microbes and viruses by interacting with membranes of infectious agents and increasing their permeability. Human antimicrobial peptides are members of either the a-defensin, β-defensin or cathelicidin families
Attenuation (of a pathogen)
The loss of pathogenicity, usually through adaptation to growth in culture in adverse conditions or in cells from a species other than that of the normal host. Attenuated pathogens are the basis of many vaccines
Avidity
Increased apparent affinity of a molecule for its ligand due to the presence of multiple binding sites on both partners
Basophils
Circulating myeloid lineage cells that are characterized by cytoplasmic granules that stain with basic dyes and contain inflammatory mediators and are believed to be important in defense against parasites as well as in inflammatory and allergic reactions
C1q
Complement component that binds to antibodies in immune complexes and activates the classical pathway of compliment activation. In addition to activating the compliment cascade, C1q is recognised by a pathogenic receptor of macrophages (C1qRp), and so can mediate phagocytosis directly
C3 convertase
Either of two proteolytic enzymes of the compliment system that cleaves the C3 to generate C3a and C3b. The C3 convertase of the classical and lectin pathways is a complex of C4b and C2b, whereas the C3 convertase of the alternative pathway is a complex of C3b and Bb
Capsular polysaccharide
Cell-surface polymers of repeating oligosaccharide units, usually linked through phosphodiester bonds that form a capsule on the surface of many pathogenic bacteria and protect bacterial cells from recognition by phagocytes. For this reason, the presence of a capsule is often associated with virulence
Cathelicidin
A family of cationic antimicrobial peptides generated in pre-pro forms that require processing to generate the active peptide; cathelicidins contain an amino-terminal cathelin-like domain and a carboxy-terminal antimicrobial domain
Chemokines
Any of a family of closely related small, basic cytokines whose main function is as chemo attractants. The name is a contraction of chemotactic cytokine
Classical pathway
compliment activation pathway through which antibody-antigen complexes trigger the complement cascade. This pathway is also activates by the pentraxins
Clonal detection
Elimination of potentially self-reactive lymphocytes. Immature lymphocytes undergo programmed cell death after binding to the antigen; in this way, cells that are bearing receptors that recognise self are deleted before they are capable of participating in immune responses. This is a major mechanism of immune tolerance
Clonal expansion
the selective proliferation of mature naïve lymphocytes that encounter antigens. Only those lymphocytes bearing receptors specifically recognizing antigen are activated to proliferate and differentiate into effector cells
Cluster of differentiation (CD)
The basis of a system for identifying cell surface molecules of immune cells by the use of antibodies and in which each molecule is given a specific number prefixed by CD to form the basis of a systematic nomenclature. The term cluster reflects the fact that each molecule is usually recognised by a group, or cluster of antibodies; and the appearance of the molecules usually reflects different differentiated states of the cell, hence differentiation. Surface marker molecules of immune cells of different types at different stages of differentiation or activation have been identified in this way and can be used to classify cells, or to follow their progression through development or their activation status
Collectin
any of a family or structurally related, carbohydrate-recognizing proteins of innate immunity, including mannose-binding lectin and surfactant proteins A and D
Complement
Serum proteins activated directly or indirectly by conserved surface features of microorganisms, or by antibody, to destroy microorganisms or induce their destruction through a coordinated immune response including induction of inflammation, attraction of leukocytes, stimulation of phagocytosis and stimulation of antibody production
Complementarity-determining region (CDR)
A region of a lymphocyte receptor for antigen that participates in the antigen-binding site and determines its structural complementarity to the antigen
Constant (C) domain
Ig-like domain of the type found in Ig constant regions. Constant region (C region): region of lymphocyte receptor for antigen that does not participate in antigen binding and does not vary between cells of different antigen specificity
Coreceptor (of T lymphocytes)
A receptor on a T cell that recognises invariant parts of MHC molecules and forms a recognition complex with the antigen receptor and contributes to the intracellular signaling
Corticosteroids
Natural and synthetic hormones that bind to and activate the glucocorticoid receptor. Corticosteroids are very effective anti-inflammatory drugs and are also immunosuppressive
