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40 Cards in this Set

  • Front
  • Back
B-cell receptors
antigen receptor on b cells,w hich is a membrane bound immunoglobulin molecule. each b cell is programmed to maek a single type of immunoglobulin . the cell-surface form of this immunoglobulin serves as the b-cell receptor for specific antigen. associated in the membrane with the immunogobluin are the signal transduciton molecules Igalpha and Ig beta
T-cell receptors
(TCR) the highly variable antigen receptor of T lymphocytes. on most t cells it is composed of variable alpha chain and beta chain. this receptor recognizes peptide antigens derived from the breakdown of proteins.
Antibodies
the secreted form of the immnoglobulin made by a B cell
Antigen
originally definded as any molecule that binds spcifically to an antibody, the term now aslo refers to any molecule or molecular fragment that can be bound by an MHC molecule and presented to a T-cell receptor
How are immunoglobulins formed?
From two different polypeptides called heavy and light chains
Structure of T-cell receptor
TCRalpha and TCRbeta, both anchored in the T-cell membrane
Difference of variable region and T-cell receptors
amino acid sequence of the variable region and t-cell receptors create many binding sites for diff antigens and diff pathogens.
clonal selection
the central principle of adaptive immunity. it is the mechanism by which adaptive immune responses derive only from individual antigen-specific lymphocytes, which are stimulated by teh antigen to proliferate and differentiate into antigen-specific effector cells
where does adaptive immune responses initiate?
specialized lymphoid tissues, lymph nodes, white pulp of the spleen, and peyer's patches of the gut
first step of adaptive immune response?
pathogen to be carried by dendritic cells from the infected site to nearest secondary lymphoid tissue
second step of adaptive immune response?
antigen loaded dendritic cells to meet and activate the small proportion of T cells with receptors that recognize pathogen-specific antigens.
who activates b cells?
effector t-cels
steps of innate immune cells alerting t-cells
1. pathogen gets access to tissue, bypassing barriers. 2. innate responses a the skin commence dendritic cell uptake 3. dendritic cells traffic to regional lymph node/secondary lymphoid organ 4. dedritic cells activate t cells 5. activated t-cells traffic to site of infection and differentiate effectors
how does t-cell receptors recognize degraded fragments?
antigens recognize by t-cell receptors are short peptides and generated by the degradation of a pathogen's proteins
antigen processing
1.dendritic cell takes up pathogen for degradation 2. antigen processing -in route to secondary lymphoid organs, DCs phagocytize and degrade pathogens 3. antigen presentation-the pieces of the pathogens are placed on MHC for T cells to try to bind to
MHC
Major Histocompatibility Complex - function is to present peptides (protein pieces) to T cells; cell surface proteins that are bound by t-cell receptors
MHC class 1
intracellular; peptides produced by the cytosolic degredation of intra pathogens are delivered to ER, where MHC class I molecules bind them and move to surface; activates CD8 cytotoxic t killer cells
MHC class 2
extracellular; first travel to endosomal vesicles, where they bind to peptides produced by lysosomal degradation of extracell pathogens, before moving to the cell surface; activates CD4 t helper cells to release immune activating cytokines
MHC class 1 have two types of effector T cells
cytotoxic t cell that defends against intracellular infection and helper t cells that defends against extracellular infection
MHC II can only be present in these cells?
DC, macrophage, and B cells
plasma cells
actviation of b cells by a pathogen leads to proliferation and differentiation of the b cells into dedicated antibody factories
native b cells
b cells that have no encountered with their antigen
receptor-mediated endocytosis
causes the bacterium to be engulfted and delivered to endocytic vesicles in the b-cell cytoplasm then killed and degraded
IgA
class of immunoglobulin having alpha heavy chains. dimetric iga antibodies are the main antibodies present in mucosal secretions. monomeric iga is present in the blood
IgD
appears as surface immunoglobulin on mature naive b cells but it function is unknown. its transcription is coordinated with that of IgM
IgE
involved in allergic reactions
IgG
most abundant class of immunoglobulin in plasma (blood)
IgM
first immunoglob to appear on the surface of b cells and the first antibody secreted during an immune response.
humoral immunity
immunity that is mediated by antibodies and can therefore be transferred to a non-immune recipient by serum.
neutralization
antibodies reduce infection by binding tightly to a site on pathogen so as to inhibit pathogen growth, replication or interaction with human cells
opsonization
the coating of the surface of a pathogen or other particle with any molecule that makes it more readily ingested by phagocytes. antibody and complement opsonize extracellular bacteria for phagocytosis by neutrophils and macrophages because the phagocytic cells carry receptors for these moelcules
somatic hypermutation
introduces nucleotide substitution throughout the variable regions of the rearranged immunoglobulin heavy and light chains. - strengthens the antigen binding properties of the antbodies
isotype switching
acts in activated b cells; improves their recruitment of effect functions
memory cells
lymphocytes that are responsible for the immunological memory
secondary adaptive immune response
adaptive immune response provoked by a second exposure to an antigen. it differs from the primary response by starting sooner and buildilng more quickly and is due to the presence of long-lived memory b cells and t cells
difference between native t cels and memory t cells
memory t cells can patrol non-lymphoid tissues and direct infection at an earlier stage
why is memory b cells better than naive b cells?
memory b cells benefit from the somatic hypermutations and isotype switching that occured in the primary response.
positive selection
process occurring in the thymus during t cell development that selects immature t cells with receptors recognizing peptide antigens presented by self- MHC moelcules. only cels that are positively selected are allowed to continue their maturation
negative selection
process in the thymus whereby developing t cells that recognize self antigens are induced to die by apoptosis
autoimmune diseases
disease in which the pathology is caused by an immune response to normal components of healthy tissues