Antibodies (year 2) Flashcards
define an antigen
any molecule that can bind specifically to an antibody or antigen receptor
define an epitope
site in an antigen recognised by an antibody or antigen receptor
define an antibody
protein that binds specifically to an antigen
what is affinity?
binding of one antigen binding fragment (Fab) region to one epitope
what is avidity?
overall attraction between antigen and antibody - able to bind to more than one epitope
what does high avidity and affinity mean for the function of the antibody?
carries out its function well, if they don’t bind well to the pathogen then they won’t work properly
what immune response are antibodies apart of?
humoral - produced by B cells
what cells produce antibodies?
B cells
name the 5 classes of immunoglobulin
IgM, IgG, IgA, IgE, IgD
where are the three main classes of antibody produced?
IgM - spleen/lymph nodes
IgG - spleen/lymph nodes
IgA - locally in mucosal systems (GI/respiratory)
what species of animal is IgD mainly found in?
fish
describe the structure of IgG
Y shaped structure with hinge regions and two antigen binding sites
describe the structure of IgM
pentameric structure with 5 subunits joined by glycoprotein bonds
describe the structure of IgA
2 subunit structure joined by a J chain
what are the two regions of an immunoglobulin subunit?
constant and variable
what is the role of the constant region of an immunoglobulin?
interacts with the hosts cells and can alter the effector function, delivers antibody to specific areas and helps to initiate the compliment cascade and when it changes it is known as class switching
what triggers class switching?
cytokines
what is the role of the variable region on immunoglobulins?
free to interact with the pathogen
what is the main isotope of immunoglobulin produced during a primary immune response?
M
what is the main isotope of immunoglobulin present during a secondary immune response?
IgG and IgA
describe the length and magnitude of primary and secondary immune responses
primary - short lived and low magnitude
secondary - rapid and longer duration with higher magnitude
why does class switching from IgM to IgG and IgA occur?
IgA and IgG have a higher affinity for antigens than IgM
where is the primary immune response initiated?
local lymph nodes
where is the secondary immune response initiated?
local lymphoid tissue
what are the two cells that synthesise antibody?
blasting B lymphocytes
plasma cells
where are the plasma and blasting B lymphocyte cells that synthesise antibody located?
in germinal centres
what are the three main functions of antibody?
neutralise pathogens
activate complement
opsonisation
what does neutralisation of pathogens prevent?
pathogen attachment
invasion of host cells
replication
toxin production
IgA is a tissue specific effector, describe this process?
secreted locally to mucosal tissue then binds to polymeric Ig receptor and passes into the lumen of the enterocyte
the receptor is then proteolysed to leave the secretory component protecting IgA
