Lecture 15 Humoral Immunity Flashcards
Antibody effector functions
Neutralization;
Opsonization;
Complement activation
BCR functions
- Initiate signal cascade by binding antigens
- Deliver antigen to intracellular sites for processing/presentation (MHC II)
What are the two ways B cells can be activated?
thymus-dependent antigens
thymus-independent antigens
Follicular helper T cells help with ______ and _________. This process takes _______.
affinity maturation and class switching; longer
_____ antigens cause B cells to activate quickly. It is ___ specific.
thymus-independent; not
The primary response of B cells occurs in ___ phases
2
Phase 1 of the primary response involves
antigen encounter;
Bcell Tcell interaction; B cell proliferation
What is involved of Phase 2 of the B cell response?
somatic hypermutation; class switching
What signals do TFH send to B cells to activate them/control differentiation?
CD40:CD40L
IL21
CD21 and CD19
What does CD40:CD40L interaction do to B cells?
activates NFkappaB and enhances survival (anti-apoptotic Bcl-2)
IL21 signaling in B cells
activate STAT3, enhances proliferation and differentiation into plasma cells and memory B cells
CD21 and CD19 interact with
C3b
The concept of linked recognition is
T and B cells respond to the same antigen (can be distinct but linked)
T cells in T cell zones have ____ receptors and respond to ____ and ____
CCR7;
CCL19 and CCL21
B cells in B cell zone have ____ receptors and respond to _______, expressed by follicular dendritic cells
CXCR5;
CXCL13
structure/function of follicular dendritic cells
octopus, lots of arms/projections, it acts as a net not a phagocytoser and traps B cells
When B cells are engaged they begin to upregulate _____ and move halfway to meet with active TFH (who begin to express _______). After communication, they _________
CCR7; CXCR5; downregulate
Resting B cells -> ______ -> plasma cells
plasmablasts
resting B cells do not have a high rate of _____
Ig secretion
Plasma cells cannot
grow, class switch, do somatic hypermutation
plasma cells have high surface ___ and _____ and low surface _____
IgA and E;
IgG
Structure of germinal center
light zone, dark zone, mantle
B cells proliferate at the highest rate in the _____ zone
dark
Many TFH cells are present in the ____ zone
light
cyclic reentry into the dark zone occurs due to _____ expression (responding to _____)
CXCR4; CXCL12
B cells undergo somatic hypermutation in the ___ zone. They drop _____ expression and migrate into the ____ zone.
dark;
CXCR4;
light;
_______ are present in GC with the antigen they caught. They can present to B cells with high affinity for the antigen (due to ________)
Follicular DCs;
affinity maturation
TFH will send _____ signals to B cells that present the antigen to them(_________). B cells that receive this signal will reenter the ___ zone and continue to mutate.
CD40 (survival);
cross link
dark
_____ made by TFH direct class switching
cytokines
_____ direct isotypes IgG1, IgE
IL-4
IFN-gamma directs _____ and _____
IgG3 and IgG2a
_______ directs IgG2b and IgA
TGF-beta
______ directs IgG3, IgG1, and IgA
IL-21
IL5 directs ____ and ______
IgG1 and IgA
Which antibodies activate complement system?
IgM
IgG3 and IgG1
_____ can transport across epithelium
IgA (dimer)
Which antibodies involved in neutralization?
IgGs and IgA
sensitation of mast cells antibody
IgE (G1 and G3 to some extent)
diffusing into extravascular sites
IgGs and A (monomer)
opsonization antibody class
G1, G2, G4ish, Aish
transport across placenta antibody class
IgG1 and IgG3
somewhat G2 and G4
_____ has secretory component that binds to polymeric Ig receptor (pIgR)
IgA
IgA and IgG can neutralize ______ and ________
bacterial toxins and viruses
Opsonization function
antibody dependent cellular activation antibody-virus engages Fc receptor to destroy virus
C1q can bind to _______ form of IgM (5-10% is isomeric)
planar
at least 2 IgG can cluster to bind _____
C1q
antigen:antibody complexes lead to activation of _______ and deposition of ____. _____ can bind and phagocytic cells in the liver and spleen can dispose of complex
complement;
C3b;
CR1
aggregation of ig on bacterial surface leads to _______ of Fc receptors and activation of ______.
cross linking; macrophages
Fcgamma R3 receptors on NK cells recognize antibodies ___ and ___ bound to target cells through ___________
G1 and G3;
antibody-dependent cell mediated cytotoxicity
Mast cells and basophils bind IgE via ________ receptor for ________
Fc-epsilon,
parasitic infections
