L7 Flashcards
what is an antigen/immunogen?
substance which provokes an immune response . usually is a foreign body
antigen is usually a protein/ polysaccharide present on cell surface or secreted by infecting organism
why type of proteins are immunoglobulins ?
glycoproteins (carbohydrate attached to them)
what produces immunoglobulins ?
plasma cells produce immunoglobulins in response to an immunogen
what is the function of the antibodies ?
neutralize antigen or kill the antigen bearing foreign cells
describe the immunoglobluins general structure.
has 2 heavy chains , 2 light chains and a variable region which is the only thing that changes and is the antigen binding side.
what parts of the antigen do immunoglobulins bind too?
Each Immunoglobulin binds specifically to one or few closely related parts on the antigen called epitopes
are epitopes on antigens limited to only 1?
no there can be a large number of them so a large number of different antibodies bind to 1 antigen
what is an epitope?
an epitope is the portion of the antigen that is recognized by the antibodies .
Binding of the antibody to an antigen also results in effector functions
Such as:
Fixation of some other proteins (complement proteins) which help in lysis of foreign organism/cells.
Release of active molecule (cytokines) from cells like mast cells and eosinophils.
Binding to cells like macrophages, neutrophils increasing phagocytosis by opsonization.
what does the complement system comprise of?
20 proteins which are present in plasma . it is involved in the defense of the body along with the immunoglobulins . also involved in cell lysis and inflammation
what are domains and what are the domains of each chain in the immunoglobuin ?
domains are globular regions . each domain has an intra chain disulfide bond .
light chain domains are VL and CL
heavy chain domains are VH, CH1- and CH3
carbohydrates are attached to the CH2 domain
what are hypervariable regions ?
regions found on the variable region of both heavy and light chains
what are the 5 classes of immunoglobulins and what are these separations based on
immunoglobulins are divided inot 5 classes based on type of heavy chain present and they are
IgG: Gamma heavy chains IgM: Mu heavy chains IgA: Alpha heavy chains IgD: Delta heavy chains IgE: Epsilon heavy chains
IgA and IgG have further subclasses with minor differences.
Light chain types can be Kappa or Lambda in any of the immunoglobulins.
discuss the igG immunoglobulin .
main antobody of serum
produced in secondary response (if person has come across this disease before )
crosses placenta and gives immunity to fetus and new born .
discuss the igM immunoglobulin .
pentamer (all other immuno globulins have 2 chains, dimers )
produced during primary response
does not cross placenta
discuss the igA immunoglobulin .
major antigen in secretions such as tears , saliva , and mucus and it protects pathways of the body
discuss the igD immunoglobulin .
found in low levels of serum
found on surface of B cells
not much is known about their function
discuss the igE immunoglobulin
involved in allergic reactions
binds tighly to basophils and mast cells
defends against helminth infections
Each person is capable of generating antibodies directed against perhaps 1 million different antigens.
How does the body manage to make so many different antibodies to all the antigens it encounters?
Antibody diversity depends on gene rearrangements.
Each immunoglobulin light chain is a product of three genes which can be joined in different combinations.
Variable region gene (VL) Joining region (J) Constant region (CL) gene
Similarly, each heavy chain is a product of four genes which are joined in various combinations
Variable region (VH) Diversity region gene (D) Joining region (J) Constant region (CH) gene
