01/21/08 1 Characteristics of Adaptive Immunity Antigenic specificity. Diversity- can recognize > billion different antigens. Specificity & Response increases & improves as it is being mounted. Immunological Memory Self vs nonself recognition.
01/21/08 1
Characteristics of Adaptive Immunity
Antigenic specificity.
Diversity- can recognize > billion different antigens.
Specificity & Response increases & improves as it is being mounted.
Immunological Memory
Self vs nonself recognition.
01/21/08 2
Specificity is achieved by Ig & the TCR.
01/21/08 3
01/21/08 4
Functional gene composed to two or more gene segments joined together.
The diversity of the Ig & TCR is generated
by gene rearrangement.
A lymphocyte prior to development:
01/21/08 5
B cells stimulated by antigen will have increased diversity through
somatic mutations.
Provides diversity & increases specificity of Ig!
Point mutations
01/21/08 6
How does the immune response amplify & remain specific towards a pathogen?
Early theories:
Friedrich Breinl & Felix Haurowitz, 1930sInstructional Theory-
Paul Ehrlich, early 1900s:Selective theory: “Cells in the blood express side chain receptors that will react with infectious agents and inactivate them.” Kuby, Immunology
Macfarlane Burnet, 1950s:Further defined Ehrlichs selective theory into the clonal slection theory
01/21/08 7
Clonal Selection Theory
Memory is achieved by the “memory cells”
01/21/08 8
Fig. 1.15, Janeway (p. 16): The 4 basic principles of the clonal selection theory.
?
01/21/08 9
How does the immune system prevent
recognition of self?
Tolerance: occurs in the primary lymphoid tissue by positive* & negative selection of lymphocytes.
Clonal DeletionAnergy
* Not shown
01/21/08 10
Apoptosis:Protease (caspases)
are activated.
DNA degradation.
Nuclear membrane integrity compromised.
Organelle/cell shrinking.
Blebbing
01/21/08 11
Kuby, Immunology
Apoptotic lymphocyteHealthy lymphocyte
How do B cells & T cells recognize & bind to antigen?
01/21/08 13
bacterium
B cell
01/21/08 14
APC
Antigen must be presented
to T-cells.
01/21/08 15
Antigen Presentation to T-cells
MHC class I Expressed on all nucleated cells.
MHC class IIExpressed on Professional Antigen Presenting Cells (APCs):
MφDCB cells
Other cells types can be induced to express MHC II.
01/21/08 16
Antigen must be processed to be displayed on MHC.
alpha betaalpha
B-2 microglobulin
01/21/08 17
The Endogenous Pathway:MHC class IEndogenous Ag:
derived from pathogens that multiply intracellularly.
01/21/08 18
Exogenous Pathway
MHC class IIExogenous antigen:
derived from pathogens that multiply outside of host cells or inside the phagolysosome.