imm 3 Flashcards
What are antibodies composed of?
They are Y shaped molecules copses of 2 light chains and 2 heavy chains
How heavy are the heavy chains that make up antibodies?
50 kDa
How heavy are the light chains that make up antibodies?
25 kDa
What hold the 4 polypeptide chains together in antibodies?
Disulphide bonds
What specifically do the disulphide bonds link in antibodies?
2 disulphide bonds link the heavy chains1 disulphide bond links each light chain to its heavy chain partnerSo 4 disulphide bonds in total
What are the 2 main groups of functions antibodies have?
- To recognise and bind antigens| 2. To elicit effector functions
Name the 2 different regions of the antibody
- The variable region| 2. The constant region
What function does the variable region complete?
It provides the antigen binding function of the antibody
2 binding sites
What function does the constant region complete?
It elicits the effector function (eg recruits additional immune cells OR cells to destroy pathogens following antigen binding)
Where are the variable region found?
At the amino (end) terminals of the polypeptides
Where are the constant region found?
At the C terminus
Define affinity
The strength of binding of one molecule to another at a single site
Give an example of an event that shows affinity
The binding of a monovalent Fab fragment of antibody to a monovalent antigen
Define avidity
The sum of the strength of bonding of 2 molecules or cells to one another at multiple sites
Antibodies are bifunctional. What does this mean?
It means they have 2 functions:1. To recognise and bind antigens2. To elicit effector functions
How are antibodies digested?
By different proteases
What has the digestion of antibodies allowed us to do?
Dissect antibodies an be able to view them at a molecular level to see what bit does what function
Name the 2 enzymes that perform important digestive functions
- Papain| 2. Pepsin
What does papain do?
It cleaves the antibody to produce 2 Fab fragments and 1 Fc fragment
What does a Fab fragment do?
It recognises the antigen
Why is the Fc fragment given this name?
It is the easiest fragment to crystallises| fragment crytaliseable
Why is the Fab fragment given this name?
Means fragment antibody binding
What does an Fc fragment do?
It binds to cell receptors to recruit other ells of the immune system
What does pepsin do?
It cuts the antibody to give a F(ab’)2 fragment