Chapter 7 and 8- Humoral Immunity Flashcards
what are the phases of the humoral immune response
- antigen recognition
-activation of B lymphocytes
-proliferation - differentiation
- outcome
what are the outcomes of the humoral immune response
-antibody secretion
- isotype switching
-affinity maturation
- memory B cell
describe T -dependent vs T-independent antibody responses
-T-dependent: isotype switched, high affinity antibodies, memory B cells and long lived plasma cells
- T-independent: mainly IgM, low-affinity antibodies, short lived plasma cells
describe the differences between the primary antibody response and the secondary antibody response in terms of lag after immunization, peak response, antibody isotype, and antibody affinity
- lag after immunization: primary is 5-10 days, secondary is 1-3 days
- peak response: primary is smaller, secondary is larger
- antibody isotype: primary is usually IgM>IgG, secondary is relative increase in IgG and sometimes in IgA or IgE
- antibody affinity: primary is lower average affinity and more variable, secondary is higher average affinity
what is receptor clustering
2 or more receptors bound to antigens
what are the transcription factors in antigen receptor mediated signal transduction in B lymphocytes
-Myc
- NFAT
-NK-kappaB
- AP-1
what does C3a do
inflammation
what does C3b do
opsonization and phagocytosis
what does C5a do
inflammation
what does C6-9 do
lysis of microbe
what is C3b cleaved into and what does it act on in B cell activation
cleaved into C3c and C3d and acts on CR2
what is complement receptor CR2 bound by
3Cd bound to microbe
what is TLR bound by
PAMP
what are the functional consequences of antigen receptor mediated B cell activation
- increased survival and proliferation
- interaction with helper T cells
- responsiveness to cytokines
- migration from follicle to T cell zone
- antibody secretion
what are the sequence of events in helper T cell dependent antibody responses
T cell zone to B cell zone
describe the process of antigen presentation to B lymphocytes to helper T cells
- B cell recognition of native protein antigen
- receptor mediated endocytosis of antigen
- antigen processing and presentation
- T cell recognition of antigen
what do activated T cells that recognize antigen presented on B cells use to activate the B cell
the CD40 ligand and cytokines
describe the germinal center reaction
-activation of B cells and migration into germinal center
- B cell proliferation
- somatic mutation and affinity maturation; isotype switching
- exit of high affinity antibody secreting cells and memory B cells
what is the function of IgM
complement activation
what does IgG do
phagocyte responses, complement activation, neonatal immunity
what induced IgE from the B cell and what is its function
- IL-4
- immunity against helminths
- mast cell degranulation - immediate hypersensitivity
what induces IgA and what is its function
-cytokines produced in mucosal tissues
- mucosal immunity
describe switch recombination
previously formed VDJ exon recombines to become adjacent to a different constant region gene
what is AID and what does it do
activation- induced deaminase
- alters nucleotides so they can be cleaved by other enzymes allowing S regions to be brought together
what does repeated exposure to a protein antigen drive
creation of higher affinity antibodies
what do FDCs do
present antigen via antibodies bound to Fc receptors or complement receptors instead of MHC molecules
are antigens internalized by FDCs
no
describe the selection of high affinity B cells in germinal centers
- B cell activation by protein antigen and helper T cells
- B cells with somatically mutated Ig V genes and Igs with varying affinities for antigen
- B cells with high affinity membrane Ig bind antigen on FDCs and present antigen to helper T cell
- B cells that recognize antigen on FDCs or interact with helper T cells are selected to survive, other B cells die
describe the chemical nature of T dependent and T- independent antigen
- T-dependent: proteins
- T-independent: polymeric antigens, polysaccharides, glycolipids, and nucleic acids
describe isotype switching, affinity maturation, plasma cells, and secondary response of T dependent and T-independent antigens
-isotype switching: T dependent-yes. T-independent: low level switching to IgG
- affinity maturation: T dependent- yes. T-independent: little or no
- plasma cells: T dependent- long lived. T-independent: short lived
- secondary response: T dependent: yes. T- independent- only seen with some polysaccharide antigens
when is the humoral response terminaated
once sufficient quanitities of IgG are produced to result in this combination of binding on a B cell
describe the mechanism of antibody feedback
- secreted antibody forms complex with antigen
- antigen-antibody complex binds to B cell Ig and Fc receptor
- inhibition of B cell response
- block in B cell receptor signaling
what are the effector functions of antibodies
- neutralization of microbes and toxins
- opsonization and phagocytosis of microbes
-antibody dependent cellular cytotoxicity - lysis of microbes
- phagocytosis of microbes opsonized with complement fragments
- inflammation
- complement activation
describe the process of antibody mediated opsonization and phagocytosis of micorbes
- opsonization of microbe by IgG
- binding of opsonized microbes to phagocyte Fc receptors
- Fc receptor signals activate phagocyte
- phagocytosis of microbe
- killing of ingested microbe
what immune response is the complement system a part of? the classical pathway?
complement: innate immune response
classical: adaptive immune response
what does the complement pathway start with
recognition of antigen engaged antibodies by complement C1 protein
what are the functions of complement
- phagocytosis and killing of microbe
- osmotic lysis of microbe
- destruction of microbes by leukocytes
what are examples of T- dependent cells? T-independent
T-dependent: follicular B cells
T- independent: B-1 cells, marginal zone B cells
