Glossary 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
alveolar macrophages
macrophages in the lungs
antibodies
highly variable proteins produced by B lymphocytes of the immune system and that recognise antigen and target it for destruction
Antibody-dependent cellular cytotoxicity (ADCG):
a process whereby FcR-bearing celts 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 receptors 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 epidemic infections.
shift
(of influenza virus) reassortment of independent RNA segments from two different influenza genomes to generate 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 MHC molecules and their presentation the cell surface for recognition by T cells
APC
cells capable of displaying antigen for recognition by T-celts 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 u-defensin, $defensin or cathelicidin families
Attenuation
(of a pathogen) loss of pathogenicity, usually through adaptation to growth in culture in adverse conditions or in cells irom 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 characterised by cytoplasmic granules that stain with basic dyes and contain inflammatory mediators and are believed to be important in defence 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 complement activation. ln addition to activating the complement cascade, Clq is recognised by a phagocytic receptor of macrophages (C1qRp), and so can mediate phagocytosis directly
C3 convertase
either of two proteolytic enzymes of the complement system that cleave 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
Cathelicidins
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
chemokine
any of a family of closely related small, basic cytokines whose main function is as chemoaftractants. The name is a contraction of chemotactic cytokine
classical pathway
complement activation pathway through which antibody-antigen complexes trigger the complement cascade. This pathway is also activated by the pentraxins
clonal detection
elimination of potentially self-reactive lymphocytes. lmmature tymphocytes undergo programmed cell death after binding to 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 naive lymphocytes that encounter antigen. Only those lymphocytes bearing receptors specifically recognizing antigen are activated to proliferate and differentiate into effector cells
clonal selection
the process whereby potentially self-reactive lymphocytes are eliminated during ontogeny whereas mature lymphocytes recognising non-self antigens are selectively expanded
Cluster of differential (CD)
the basis of a system for identifoing cell surface molecutes of immune cells by the use of antibodies and in which each molecule is given a speciflc 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 and at different stages of differentiation or activation have been identified in this way and can be used to classifiT cells, or,to follow their progress through development or their activation status.
collectin
any of a family of structurally related, carbohydrate-recognising 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, aftraction of leukocytes, stimulation of phagocytosis and stimulation of antibody production
Complementarity-determining region (CDR):
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:
lg like domain of the type found in lg 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 specificities
coreceptor: (of T lymphocytes)
(of T lymphocytes) receptor on a T-cell that recognises invariant parts of MHC molecules and forms a recognition complex with the antigen receptor and contributes to intracellular signalling.
Corticosteroids:
natural and synthetic hormones that bind to and activate the glucocorticoid receptor. Corticosteroids are very effective antiinflammatory drugs and are also immunosuppressive.
C-type lectin
ell-surface or secreted protein that is characterised by a conserved three-dimensional fold and somewhat conserved amino-acid sequence and that binds to carbohydrate ligands, typically in a calcium-dependent manner.
C-type lectern receptor
cell-surface proteins containing C-type lectin domains that do not bind carbohydrate ligands and are thus distinct from Ctype lectin receptors; C-type lectin receptors commonly mediate phagocytic or endocytic uptake and/or signalling into the cell
Cytokine
polypeptide signalling molecules that participates in immune responses. Cytokines often act locally (in an autocrine or a paracrine manner) but can act systemically. Most cytokines are secreted molecules, but membrane-bound versions also occur in most cytokine types
cytotoxic T cell
T lymphocytes specialised to kill cells infected with pathogens that replicate in the cytoplasm
Dectin-1
a phagocytic C-type lectin receptor recognising microbial B-glucan polysacch
defensins
any of a family of cationic antimicrobial peptides of vertebrates with three disutfide bonds and a largely beta-sheet structure.
dendritic cells
specialised cells that ingest debris and infectious agents in the peripheral tissues and migrate to lymphoid tissues where they present fragments of the ingested particles for recognition by T lymphocytes in the activation of adaptive immune responses. Some dendritic cells are resident in ihe lymphoid tissues and function as phagocytes there before differentiating into antigen-presenting cells
effector cells
cells that are quipped to activate or destroy other cells directly
ELIZA
a technique for measuring the amount of a molecule in a sample in which the antigen is put or trapped on a solid support and then an antibody with an attached enzyme is used to bind to the trapped antigen. Alternatively, an ELISA can be used to measure the amount of a specific antibody in a sample. The amount of enzymatic activity is direcfly related to the amount of the antigen or antibody on the plate
Eosinophils
cells containing cytoplasmic granules that stain with a dye eosin and contain inflammatory mediators that are released on activation by T cells or antibody-coated parasites
epitope
molecular feature of an antigen that is specifically recognised by a lymphocyte or an antibody.
Fab fragment
fragment of an antibody generated
Fc fragment
immunoreceptors that mediate many of the effects of antibodies. These receptors are so named because the part of the antibody molecule they recognise is called the Fc region. ic receptors mediate cellular functions such as phagocytosis, cell killing, and degranulation
heavy chain
the immunoglobulin heavy chains are the larger of the two kinds of polypeptide chains in the immunoglobulin molecule. Each light chain has a variable region contributing to’the’antigen-binding site, and a constant region that mediates the effector function of the molecule.
hemagglutination
the property by which antibodies binding to red blood cells cause them to agglutinate
Hemagglutinin:
influenza homotrimeric envelope piotein that binds to widely distributed host-cell-surface glycoproteins and glycolipids that are modified by sialic acid additions and is required for virat entry to host.
Hematopoietic stem cell (HSC):
self-renewing cellthat gives rise to all the red and white blood cells
‘Highly pathogenic avian influenza (HPAI):
influenza viruses with high virulence for chickens and other birds. These viruses commonly express H5, H7, H9 hemagglutinin proteins with an expanded basic amino- acid repeat that increases the ease of proteolytic diggstion required to activate the fusion domain
