9/2/10 Antibodies And Vaccination

Front 1

Describe and give at least one example of each of Hypersensitivity Types II and III

Back 1

Type II: Antibody-mediated (not IgE)
Phagocytes (neutrophils, macrophages) are recruited
(i.e. attracted by C5a/C3a) and activated (i.e. by antibody binding to FcgRI, or C3b to CR1)

Tissues injured by “frustrated” phagocytosis*

Examples: (myasthenia gravis, transfusions)


Type III: Immune complex-mediated (immune complex is a complex of antigen/antibody/complement)
Like Type II, phagocytes recruited/activated->tissue injury

Examples: (poststreptococcal nephritis, SLE)

Front 2

Explain the differences in the antibody response between the primary and secondary exposure to an antigen

Back 2

Primary: naive activated by antigen, response generates some memory cells

Secondary: activate from memory cells, no igM, higher affinity for antigen

Front 3

Describe affinity maturation, including the role of somatic hypermutation, follicular dendritic cells and B cell selection in germinal centers

Back 3

Follicular dendritic cells (FDCs): only found in germinal centers of lymphoid follicles. Unlike regular DCs, FDCs do not express PRRs or internalize antigens or express MHCII or produce IL-12. What they do is grab onto immune complexes using Fc and complement receptors (FcgammaR1 and CR1/CR2)

Late in any response, FDCs are the last cells that still have antigen

B cells in germinal center must outcompete each other to bind antigen on FDCs in order to survive. To gain selective advantage, germinal center B cells undergo somatic hypermutation.

Front 4

Somatic Hypermutation involves...?

Back 4

AID* (the enzyme from isotype switching ) helps introduce point mutations in V regions of heavy/light chains of BCR

B cells with mutations that improve affinity for antigen, grab antigen from FDCs, process/present MHCII:peptide complexes to TH cells in germinal center, differentiate into either memory cells or plasma cells, that will secrete high affinity antibody

In secondary response, memory cells quickly reactivate and produce high affinity antibody (these reactivated cells undergo another round of somatic HYPERMUTATION so that antibody affinity in tertiary response is even higher!!!)

Front 5

Describe the development of T-independent antibody responses including the role of the spleen

Back 5

Follicular B cells: t-dependent Ab response

Marginal Zone B Cells (white pulp of spleen): t-independent

T-independent antigens are non-protein antigens with repeating structures

When this antigen binds/cross links enough BCRs on a splenic marginal zone B cell, B cell is activated/matures into antibody-secreting plasma cell (without T cell help!!!!!)

Front 6

Compare T-dependent and T-independent antibody responses with respect to the nature of the antigen, important lymphoid organs, affinity and isotype of the antibody, and memory

Back 6

Protein vs Polysaccharide
Switched isotypes vs IgM
High affinity vs Low
Lymphoid follicles vs Marginal Zones
Memory vs no memory
Affinity maturation vs no maturation

T independent not well developed in infants (thus no polysac. vaccines)

Conjugation turns T-independent antigen into T-dependent antigen

Front 7

Define the terms hapten and carrier, and draw the process of B and T cell collaboration that results in a T-dependent antibody response to a conjugated hapten or polysaccharide antigen

Back 7

Hapten: small chemical that can bind to Ab but does not elicit response. When hapten is linked to carrier, Ab response specific for hapten occurs.

BCR binds hapten attached to protein. Presents on MHC and activates T cell. Makes Ab specific for hapten.

Helps immunize against polysaccharides (have to conjugate to protein) - makes t-independent into t-dependent

Front 8

Distinguish between active and passive immunization and compare the types of vaccines used for active immunization

Back 8

Vaccines with attenuated viruses, viral vectors or DNA vectors (DNA enters cells, proteins are produced intracellularly) can stimulate both cell-mediated immunity (including CTLs*) and antibody responses

Vaccines with only proteins or polysaccharides stimulate mainly only antibody responses

Recombinant proteins are called synthetic vaccines. Parts of microbes (proteins or polysaccharides) are called
subunit vaccines


Toxoids are subunit vaccines that are inactivated toxins (formalin-treated) i.e. tetanus vaccine

TDap = subunit vaccine (2 toxoids + pertussis protein)

Front 9

Describe the effects of adjuvants on the immune response to a vaccine

Back 9

Adjuvant: a substance distinct from the antigen that enhances T cell activation by promoting accumulation of antigen-presenting cells (APCs) at the antigen site, and expression of costimulatory molecules and cytokines by APCs

Alum (aluminum salts) is classical human vaccine adjuvant

Antigens absorb to it and elute slowly after injection
Alum is an irritant, causes leukocyte recruitment

Adjuvants not necesssary for killed or attenuated microbial vaccines

Front 10

Distinguish between a polyclonal and a monoclonal antibody response to an antigen

Back 10

Monoclonal Abs: from 1 B cell, heavy and light chains of each Ab molecule are identical, used therapeutically or diagnostically

Polyclonal: from several original B cells bc antigens have several epitopes. Normal responses all polyclonal. (malignant clone of plasma cells produce monoclonal Abs-diagnostic)