Physiology Review
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Jena Giltnane
2/8/06 Section 3
Madri Discussion Paper: Shen, et al Science (304) 2004
endothelial cells secrete factors that prevent differentiation of neural stem cells and creates a “neural stem cell niche” that these cells live in.
These cells are then a pool of dividing cells that differentiate into neurons and glial cells.
Immunology Lectures Review
Cells
T-cells
the T cell Receptor (TCR) on the T cell recognizes both the MHC molecule and the peptide bound to it
MHC Molecules (aka “HLA”)
Class I – on virtually all cells, present endogenous antigen to CD8 (killer) T-cells
Class II – on APCs, present exogenous antigen to CD4 (helper) T-cells
Antigen Presenting Cells acquire, process and present antigen
Dendritic cells, macrophages, B-cells
Mast Cells
IgE is bound to the surface of mast cells
when these IgE molecules bind to their specific substrate, this leads to DEGRANULATION of the mast cells, releasing vasoactive amines (e.g. histamine)
Plasma components
Complement cascade
complement proteins bind to the surface of foreign objects
direct killing of microbes
opsinization (for clearance by macrophages
formation of the MAC
Antibodies
Abs have two identical variable regions, both of which can bind to a ligand with extremely high affinity
Therer are five types of antibodies:
the variable region determines the specificity of the Ab
the constant region determines the effector function
Abs are the secreted form of the B cell receptor (BCR)
Antibodies come in essentially 5 flavors:
activated B cells differentiate into PLASMA cells
FUNCTION to secrete antibodies
Concepts:
Adaptive Immune Response
if an infection cannot be cleared quickly by the action of PMNs and macrophages, the adaptive immune response is elicited
this involves APCs that carry antigens from the site of infection to a draining lymph node T cells and B cells are activated
secreted Ab and activated T cells can then move from the lymph to the blood and back to the site of infection for clearance of the infection
Tolerance
the specificities of the variable regions of the TCR and the BCR (and thus Abs also) are generated in a random fashion
CENTRAL TOLERANCE self-reactive lymphocytes are DELETED during lymphocyte development
T cells in the thymus
B cells in the bone marrow
ANERGY (PERIPHERAL TOLERANCE) self-reactive T cells that leave the thymus can then be “inactivated” once they reach the peripheral tissues. This inactivated state = anergy
Hypersensitivity
consists of an immune response directed against NON-INFECTIOUS agents
innocuous particles, proteins, etc.
examples seen in: pollen allergies, food allergies, drug allergies, etc.
self proteins
leading to autoimmunity type I is generally not implicated in autoimmunity, while types II, III &IV are NOTE: autoimmunity is utterly dependent upon the adaptive immune response
4 types of hypersensitivity can be delineated:
Anaphylactic/IgE-mediated allergic rhinitis, food allergies and systemic anaphylaxis
Cytotoxic: mediated by IgG directed against cell- or matrix-associated antigens autoimmune hemolytic anemia, Graves disease, myasthenia gravis
Immune complex-mediated – IgG antibodies are directed against soluble antigens, leading to the formation of immune complexes
systemic