BIOL 435 Ch. 12 p.1 (Effector Responses) Flashcards
antibodies
- can mediate the destruction and clearance of a pathogen in a variety of ways
- each isotope has distinct properties and traits
Ab-mediated effector functions
- Neutralization
- Agglutination
- Opsonization
- Complement activation
- ADCC
- AD degranulation and mediator release
neutralization
- protects against viral or bacteria infection or damaging effects of toxins
ex. prevents viral entry into target cells
agglutination
-enhances neutralization
-more efficient clearance of pathogens from body
-cross-links pathogens
>clumping and more efficient phagocytosis
opsonization
- promotes and/or enhances the engulfment of Ags by phagocytes
- makes pathogens ‘more tastey’
complement activation
-classical pathway
-results in generation of MAC
>creates pores in pathogen membranes and kills the microbe
ADCC
- Ab-dependent cell-mediated cytotoxicity
- activates killings activity of several types of cytotoxic cells (eg. NK cells)
eg. Fc portion may be available
AD degranulation and mediator release
-triggers mediate release from granulocytes
ex. allergies (worms)
>IgG binds worm and Fc binds to granulocytes
IgM
-membrane bound naive B cell
-secreted from activated B cells
-first Ab produced in primary response
>relatively low affinity
-pentameric (10 total Ab binding sites): high avidity
IgM function
- very good at complement fixation leading to MAC and target lysis
- efficient at forming dense Ab-pathogen complexes which will be engulfed by macrophages
IgG
- most common in serum
- several subclasses: each with different capabilities
- all bind Fc receptors and act as opsonins
- activate complement
- mediate ADCC
IgA
- major Ab in secretions
- neutralizes toxins and pathogens
- does not fix complement: does not drive inflammation
- long half life
- good at agglutination
IgA in blood
-can stimulate:
>phagocytosis
>ADCC
>trigger degranulation of granulocytes
IgA long half life
- in secretions
- due to protease-resistant AA sequence in Fc region
IgA in secretions
- gut
- respiratory
- reproductive tracts
- tears
- saliva
- breastmilk