Antibodies and complements Flashcards
what is the difference b/w the primary and secondary response to an antigen
secondary is much more powerful and faster
basis of vaccinations*
what are the 3 basic functions of Ab ?
1 - opsonization (tag/label)
2 - complement fixation (once activated will destroy)
3 - direct nuetralization (bind and remove toxins)
what is the major isotype of immunglobins in blood serum ?
IgG
basic functions of IgG
- neonatal immunity
- immunological memory
what is the basic structure of ALL Ab ?
Y shaped
Function of IgD and what percentage of blood serum does it make up ?
B cell receptor, so major Ig at surface of B cells
-rare in blood <1%
How much of IgE is in blood and what is its function
Scarce
- found on surface of basophils and mast cells
- kills lg. parasites
- part of allergy response
what purpose do the multiple granules cells w/in mast cells serve ?
act like torpedos to attack parasites
what is the structure of IgA and where is it found
- dimer
- secreted by saliva in oral cavity
what is the structure of IgM and why does this make it unique
-pentamer, allows it to sniff out antigens the fastest cuz so many arms making it first secreted Ab to respond
what Ig can serve as B cell receptors ?
IgD
IgM
what is the general role/significance of the complement system in immune response
complete the role of Ab
how do complement fragments become active ?
- Start as proenzymes (inactive) w/masked active sites
- proteolytic cleavage unmasks exposing active site
- result in “active” fragments of complement molecules
what is the central component of complements
C3
what are known as the late components
C5-C9 (formation of the MAC)
what are the 3 principle functions of the complement system
1 - opsonization and cell activation
2 - chemotaxis
3 - lysis of target cells
what is the difference in the complement systems functions of 1) opsonization and 2) chemotaxis
1) opsonization - complement fragments tag Ag for phagocytosis “eat me”
2) chemotaxis - complement fragements stimulate immune cells to move towards infection “find me”
The complement systems ability to lyse target cells requires the assembly of what ?
membrane attack complex (MAC)
what specific complement family members perform opsonization
opsonization - IC3b, C3b, C4b,
what specific complement family member perform chemotaxiss
chemotaxis - C3a, C5a
what specific family member of the complement system performs cell-mediated cytolysis
C5b
the classical activating pathway for the complement system is part of the _____ immune response whereas the alternate pathway is part of the _____.
- adaptive (needs Ag-Ab complex)
- innate (only need Ag)
Explain the alternative activation pathway of the complement system
1 - cleave C3 = C3a and C3b
2 - in presence of Ag then C3b binds factor B = C3bB
3 - factor D cleaves C3bB = C3bBb ( C3 convertase)
4 - C3 convertase catalyzes more C3 and start over
what is C3 convertase in the alternative pathway and what is its role
C3bBb
-catalyzes tons of C3 cleavage which engages more complement framents to become activated
what occurs in the alternative pathway after C3 cleavage if no bacteria/Ag is present
1) C3b binds factor H = C3bH
2) C3bH is deactivated by factor I (inhibitory) = IC3B + H
what is C5 convertase in the alternative pathway and what is its role
Binding of C3 convertase to another C3b cell = C3bBbC3b
-cuts C5 which activates the “late component” complement system
what is the adapter component of the classical activation pathway of the complement system, how does this work
C1
- when it binds to Ab-Ag complex, undergoes conformational change (flat hand —>gay hand) and becomes activated
would C1 bind to a free Ag ? what about a free Ab ?
It would bind to neither
only bind to Ab-Ag complex
Explain the classical activation pathway of complement system
1) C1 binds Ag-Ab complex and becomes active
2) C1 cleaves C2 and C4 = C4b2a (C3 convertase)
3 C3 convertase cleaves more C3 (start over)
what is C3 convertase in the classical actiavtion pathway
C4b2a
what is C5 convertase in the classical activation pathway and what is its role
C4b2aC3b
-Cuts C5 which activates “late stage” of complement system
what does C9 do ?
needed to traverse tthe membrane to form a membrane attack complex (MAC)
what is required for the initiation of membrane attack complex (MAC), what enzyme produces this ?
C5b, C5 convertase cleaves C5=C5b
