Immunoglobulins Flashcards
Role of hypervariability region in the variable region
Complementarity determining
Can recognise variety of antigens
Chromosomes coding for Ig
Heavy chains genes coded on Chr 14
Light chains genes coded on Chr 2 and 22
Monomeric Ig
Ig D, IgE , IgG
Polymeric Ig
IgA -dimer
IgM- Pentamer
Main Ig produced in immune response
IgM
Due to pentameric structure, efficient in fixing complement and agglutination
Half life 5-10 days
Major Ig in serum
IgG
Subclasses IgG1-G4, G1 and G2 -more quantity
Predominant during secondary immune response
Imp defence against bacteria and virus
Responsible for opsonisation,activates complement
Long half life - about 4 weeks
Only Ig that can cross placenta
IgG
Role of different IgG subclasses
IgG1 - most pathogens
IgG2- against LPS,meningococcal
IgG3 -mainly against viral- RSV
Role of IgA
Major Ab in secretions (colostrum,saliva,tears),mucosal
surfaces (intestinal,genital)
IgA1 -Mostly in serum
IgA2-more in secretions, gut (mucosal immunity)
Polymeric Ig receptor transports Ig A into cell
Role of Ig E
Mediates immediate hypersensitivity
Mediates host defense against helminthic infections
Binds Fcr receptor on mast cells and basophils
Half life 1-5 days
Cytokines that influence Ig class switching
IL-10,IL-21 drive IgG1,G3
IL-4,IL-13 drive IgG4,IgE
TGF beta,IL-10 drive IgA1,A2
Region of Ig responsible for binding Ag
Fab fragment
Blocks active site of toxins/pathogen associated molecules
Region of Ig responsible for activating complement
Fc fragment
Inflammatory/effector functions of complement
Trafficking of Ag into Ag processing pathways
Placental transfer
Ig that fixes complements in alternate pathway
IgA
Ig that fixes complements on binding to antigen
IgG, Ig M
