2.4 - B Cell Immunity Flashcards
Important cytokines in activation of B cells
IL-4, IL-6 and IL-10
IL-6 and IL-10 play a role in what
the differentiation of B cells to antibody secreting plasma cells
When B cells proliferate, they can turn into
Memory cells and plasma cells
Major antibody secreting cell
Plasma cell
Yes or no for these scenarios with B cells and plasma cells: Surface Ig, Surface MHC class II and high rate of Ig secretion
B cells: Yes, Yes, no
Plasma cells: no, no, yes
Where does the B cell encounter the T cell?
Lymph node
Mature naive B cells goes to primary follicle, which then goes to ___ to look for antigen
FDC
B cell recognizes ___ portion of antigen
native
T cell recognizes ___ portion of antigen
processed
FDC expresses what receptor that C3b can bind to and remain on the cell surface
CR1 receptor
When the B cell and TfH CD4 positive T cells interact, where will they go?
- Some go to medullary cords to differentiate into plasma cells
- Others go back to primary follicle, actively divide w/ the formation of the germinal center
Somatic hypermutation occurs in what region
V region
Describe somatic hypermutation
B cells are trying to end up w/ high affinity antibodies that bind tighter
- If they have low affinity they undergo apoptosis
Apoptosis of low affinity antibodies after somatic hypermutation are engulfed by
Tingible body macrophages
IL-10 and IL-6 specific function
Make antibodies that fight and terminate current infection
IL-4 specific function
- Bring about differentiation into memory B cells
T independent antigen do/don’t require the presence of a helper T cell
Don’t
T-independent antigens contain ___ that provide both signals 1 and 2
repetitive epitopes
Examples of repetitive epitopes
lipopolysaccharides and capsular polysaccharides
Is there class switching in t-independent antigens? Why? What’s the major antibody class?
No, b/c T cells are responsible for class switching and you don’t have T cells present
IgM
Majority of antigens encounter T dependent or T independent antigens
T dependen antigens
cytokines play a role in what in T-dependent response
Play a role in which antibody isotype switching may occur
IL-4 induces ___ production
IgE
TGF-beta induces ___ production
IgA
Describe IgM
- macroglobulin
- Mainly found within vascular system
- defense against bloodborne pathogens
- bacteremias
All polymeric antibodies have J chains, including ___ and ___
IgM and IgA
Describe IgG
- major antibody class in blood and within tissues
- protects newborn b/c only class to cross the placenta
- protects against blood borne and tissue associated infections
Subclasses of IgG
IgG1
IgG2
Half life of IgG is
1 month
IgG1 function
response to protein antigens
IgG2 function
response to carbohydrate antigens
What happens when there’s an in utero infection?
- fetus can make IgM and IgG
- can make high concentration of IgM (it’ll respond to infectious agent)
At birth, how long are babies protected from infection? Then what happens?
5-6 months
Then newborns start to make antibodies and their levels are low
___ receptor is responsible for transporting IgG from blood to tissue and for crossing the placenta
FcRn
IgD function
No function
IgE function
- associated w/ allergic reactions
- important in parasitic infections
IgE receptor
FcepsilonRI
IgA function
- major antibody in external secretions
- protects mucosal surfaces
___ plays a role in active transport and has a protective effect in external secretions
secretory piece (SC)
___ can go through same process as IgA in patients that lack IgA
IgM
Steps for IgA binding to poly Ig receptor
- binding
- endocytosis into epithelial cell
- transported across cell and released through lumen of secretory gland
- receptor cleaved and IgA is bound to mucus through secretory piece
saliva contains what Ig
sIgA
gingival exudate has what Ig
- mainly IgG
- but also has IgM and IgA
Gingival or cervicular fluid IgG to IgA ratio
More IgG than IgA and has high ratio
Saliva ratio of IgA to IgG
19:1
___ can degrade S-IgA1 and make it nonfunctional
IgA protease
Describe Neutralization and what’s their Ig
antibody that neutralizes viruses or bacterial toxins
IgA and IgG
Opsonization Ig
IgG
Sensitization for killing by NK cells Ig
IgG
Sensitization of mast cells Ig
IgE
Describe the Activates complement system and what’s their Ig
also called lysins
cause disruption of cell membranes, especially in conjunction w/ the C system
IgM and IgG
Describe agglutinins and their Ig class
enhance bacterial removal
IgM
Describe opsonins and their Ig class
enhance phagocytosis
IgG
Phagocytic cells have what 2 receptor types?
Fc and C3b (CR1 or C3b receptor)
Describe anti-adherence and what’s their Ig class
- prevents attachment of microbes to cells or hard surfaces
- sIgA in saliva
4 common Fc receptors
FcRn
FclambdaRI
FclambdaRIII (CD16)
FcepsilonRI
Antibody dependent cell cytotoxicity involves NK cells which have ___ receptor
CD16
Anti-CD20 is used today of part of ___
Targeted therapy in treating patients w/ B cell leukemias and lymphomas
receptor for IgE. What’s the receptor expressed by?
FcepsilonR1
Mast cells and basophils and eosinophils
