Antibodies Flashcards
Define antibody
an antibody is a protein that is produced in response to a foreign molecule (antigen), and has the property of binding specifically to that antigen
What type of luekocytes produce antibodies?
antibodies are produced by B lymphocytes
Antibodies constitute the class of proteins known as ……………….
immunoglobulins
What are the secondary effector functions after an antibody has binded onto a antigen?
complement activation
opsonisation (promotion of phagocytosis)
cell activation via specific antibody-binding receptors (Fc receptors)
Identify the antigen binding site (Fab) and Fc portions of the molecule?
add pic
Are antibody molecules flexiable
yes
Both light chains and heavy chains can be divided into ………… regions and ………….. regions Hint: it has to do with the flexability of antibodies
variable and constant add pic
How many hypervariable regions make up the antigen binding site?
3
What region that is made up of 3 hypervariable regions within V domains forms the antigen binding site?
complementary determining region (CDRs)
Define Antibody Affinity?
Is a measure of the strength of binding between a single binding site of an antibody and its antigen
Define Antibody Avidity?
Defined as the overall strength of multiple interactions between an antibody with multiple binding sites and a complex antigen with multiple epitopes: add pic
define epitopes
the part of an antigen molecule to which an antibody attaches itself.
Briefly explain Antibody Cross-Reactivity?
Antibody elicited in response to one antigen can sometimes recognise a different antigen of similar structure: 1. Vaccination with cowpox induces antibodies which are able to recognise smallpox 2. ABO blood-group antigens (glycoproteins on r.b.c.) Antibodies made against microbial antigens on common intestinal bacteria may cross-react with carbohydrates on r.b.c.
What part of the antibody differs between different antibody classes?
Different classes of antibodies differ in the constant regions of their heavy chains: add image
List the immunoglobulin classes
IgG IgA IgM IgE IgD GAMED
What is the function of IgG?
Ig nuetralises toxins and viruses Major activator of classical complement pathway (mainly IgG1 and IgG3)
How does IgG structure help with its function?
When IgG binds to a bacterium or other infectious agent, macrophages or nuetrophils recognise their Fc (they posses Fc receptors) and this leads to phagocytosis (opsonisation)
Name the 4 sub classes of IgG?
IgG1 IgG2 IgG3 IgG4 I
Actively transported across the placenta
Name the function of IgA?
Protects mucosal surfaces from bacteria, viruses and protozoa
Nuetralise toxins- by binding ontp infectious agents it can block their infectivity- often by preventing adherence of the agents to the epithelial cells
Where does IgA occur as a mononmer and where does it occur as a dimer
Occurs as a monomer (blood) and as a dimer (secretions)
Where does the SC (secretory component) get added to the IgA and what role does it play?
add Pic of IgA The SC is added to the IgA when it passes through the epithelial cells it helps protect IgA from degradative enzymes
How does IgM structure helps with its function?
Its 5 Fab pairs allow it to bind strongly to the surface of bacteria causing agglutination
What is the function of IgD?
involved in B cell development and activation
What is IgE function and how does its structure help it carry out it function?
Mast cells and basophils have a high affinity for the Fc of IgE When IgE that is bound in this way is cross-linked by antigen, degranulation of the cells occurs with release of inflammatory mediators such as histamine. This can give rise to allergic reactions.
Lable the diagram below
