Flashcards in Humoral Immune Response Deck (57)
List the 5 classes of immunoglobins.
IgM, IgG, IgA, IgE, IgD
What are the properties and functions of IgM?
- first Ig made by fetus and B cells
-high avidity, low affinity
- present in colostrum and mother's milk (but does not cross the placenta)
- may or may not be produced during secondary immune response
What type of receptors on phagocytes binds IgM?
What are the properties and functions of IgG?
-major serum Ig (most abundant isotype in serum)
-major immunoglobulin of secondary immune response
***is transported across the placenta
- fixes the complement
What is the major immunoglobulin of the secondary immune response?
List the four sub-classes of IgG and how they are acquired.
the differences are different constant regions of the heavy chain
Why does IgG have a longer lasting immune response?
Which Ig can be transported across the placenta?
Which Ig's can fix the complement?
Which Ig's are opsonins?
What two forms does IgA exist?
IgA1 - monomeric
IgA2 - dimeric
Where is IgA found?
in serum and body secretions:
What two Igs are present in colostrum and mother's milk?
What is the purpose of IgE? structure?
-Fc receptor binds to basophils & mast cells causing degranulation
-parasitic infections (Helminths)
What is an important mediator in the granules?
What does histamine do?
increases vascular permeability which creates edema, hives
Where is IgD found? structure?
-on membrane of mature B cells (like IgM)
structure - monomer
What type of organisms activate the humoral response?
What are the phases of humoral response?
-B cell gets activated by one antigen
- B cell undergoes clonal expansion and differentiation
Two types (plasma & memory B cells)
Which chains on the B cell undergo rearrangement?
Which chain undergoes class switching?
Which chromosome is the heavy chain found? light chain?
heavy - chromosome 14
- chromosome 2 (kappa)
- chromosome 22 (lamda)
How do we change immunoglobulins?
triggers which cause class switching: changing of the constant regions
Distinguish between primary and secondary antibody responses.
- 5-10 day lag
- peak response is smaller
- IgM> IgG
- lower affinity
- 1-3 day lag
- peak response is larger
- IgG (IgA, IgE if heavy chain isotype switching)
- higher affinity
IgG has a higher (avidity/affinity)?
IgM has a higher (avidity/affinity)?
Which segment gets deleted in class switching?
Which B cells are T-dependent?
follicular B cells
Which B cells are T-independent?
Marginal zone B cells
B1 B cells
Which B cells are able to class switch?
T-dependent follicular b cells
T-independent B cells are mainly what type of Ig?
Where will you find the CD5 marker?
B-1 B cell; not specific
T dependent activation is due to a CD40 ligand binding to a B cell's ___.
What type of antigen is present when class switching is activated?
What type of antigen is present in T-independent activation?
polysaccharides, nucleic acid, lipids
In what part of the spleen will B cells be?
After a splenectomy, an individual will be susceptible to which organism?
What is Hyper IgM syndrome?
- can only produce IgM
-results from mutations affecting class switching
What recognition is required between a Tcell and Bcell for class switching?
Cd40L - CD40
CD28/B7 (CD 88)
Th1 releases cytokines IL4 / IL4R ----clonal expansion
What would you expect if a Tcell did not have CD40 ligand?
- repeated chronic infections
-elevated IgM but no class switching
- no secondary response available
What happens when FasL is activated?
cell undergoes apoptosis
-important if there was a defective FasL (lymphoproliferative syndrome)
What are the three pathways of the complement cascade?
Classical Pathway (antigen antibody complex)
MB-Lectin Pathway (lectin binding on pathogen surface, )
Alternative Pathway (polysaccharides found on bacterial cell wall)
How are the complement cascades different?
activation is different
Where are complements produced?
liver; problems with liver can give you complement problems
Which complement protein has 3 subunits?
Describe the process of the classical pathway.
1. Once antibody is bound to antigen, a receptor will bind to C1q. Once complex is bound to C1q, it will activate C1r and then C1s.
2. Activates C2 and C4. Cleaves subunits C2a, C2b, C4a, C4b
3. C4b and C2b will make C3 convertase.
4. C3 is cleaved. C3b, C4b, C2b make C5 convertase.
5. C5 cleaved and then C6-9 are added to make MAC complex.
Describe the process of the lectin pathway.
1. Mannose binding lectin causes C4 and C2 cleavage.
2. C4b and C2b will make C3 convertase.
3. C3 is cleaved. C3b, C4b and C2b make C5 convertase.
4. C5 cleaved and then C6-9 added to make the MAC complex.
Which components of the complement pathways are inflammatory mediators?
Describe the process of the alternative pathway.
1. Activated by non-protein antigens. in the presence of Factor D, Factor B will be activated
2. C3b and Bb will make C3 Convertase
2. C3 will be cleaved
3. C3b, Bb, and C3b will make C5 convertase
4. C5 cleaved and then C6-9 added to make a MAC complex
What is the function of the complement?
-phagocytosis and killing of microbe
-osmotic lysis of microbe
-destruction of microbes by leukocytes
What is the biological function of C2b?
-associate with edema & cough
What is the biological function of C3a?
What is the biological function of C3b or C4b?
opsonin - promotes phagocytosis
Where are CR1 found?
follicular dendritic cells
Where are CR2 found?
Where are CR3 and CR4 found?