15: Humoral Immunity Flashcards
Follicular vs marginal B cells
Follicular: recirculating (majority)
Marginal: in spleen for blood-borne Ags
What causes B cells to undergo anergy
B cell recognizing Ag without BCR cross linking, co-stimulatory ligands, or cytokine support
What is critical for class switching and affinity maturation to occur?
CD40-CD40L interaction
Where do affinity maturation and class switching occur?
GCs
Class switching process: 2 steps
- Th and Tfh cell cytokines open switch regions in heavy chain DNA
- VDJ gene segment recombined with downstream C region gene
Affinity maturation
AID introduces point mutations in switch regions of variable and light Ig genes -> high affinity Abs
High affinity selection checkpoint after affinity maturation
FDCs provide Ags to new BCR receptor to sample -> if higher affinity, B cell clone is selected for further differentiation
Where are long lived plasma cells found?
Bone marrow (IgG), mucosa (IgA)
Plasma cells: what cell marker increases
CD27
Anti-apoptotic marker on memory B cells
Bcl-2
What cytokine signal is required to keep memory B cells alive?
IL-7
Antibody feedback
Excess Abs bound to a pathogen will block further Ab production
Microbe neutralization: classes and purpose
Done by all Ig classes, neutralizes the infectivity of a pathogen + block pathogens from binding cell surfaces to gain entry
Which Ig is a super efficient complement fixer?
IgM
Waste management function of Abs
Opsonization -> clearance of ICs from circulation in a non-inflammatory manner
How RBCs play a role in waste management
CR1 on erythrocytes bind circulating ICs -> liver/spleen -> removal of ICs and digestion by phagocytes -> RBCs continue to circulate
ADCC: four cell types that perform it
NK cells, macrophages, neutrophils, eosinophils
ADCC
IgG or IgE bind surface-bound Ag -> NK cell binds Ab via Fc receptor and kill via lytic enzymes, TNF, and perforin/granzymes
What class does Th2 cytokines influence class switch to?
IgE
Cells that produce natural Abs against blood group Ags
B1 cells, marginal zone B cells
FcRN
Neonatal IgG receptor for recycling and transcytosis of IgG across placenta
How maternal IgG crosses placenta
IgG pinocytosed from circulation -> bound to FcRN in endosome -> translocates to fetal circulation and releases when at neutral pH
Most vulnerable period for an infant’s immune system
6-12 months
Passive immunization
Introduction of Abs or antiserum into a naive recipient
Difference between passive and active immunization
Passive: immediate, no memory
Active: lag time, makes memory
Functions of passive immunization
- Prevent disease after known exposure
- Ameliorate sx of ongoing disease
- Protect immunosuppressed pts
- Block bacterial toxins
IVIG uses
Treatment of some autoimmune and inflammatory diseases
Monoclonal Abs
Highly specific epitope recognition -> stimulates a variety of immune responses -> come with side affects
Uses of monoclonal Abs
Cancers, autoimmune diseases
