Physiology Review

Jena Giltnane

2/8/06 Section 3

Madri Discussion Paper: Shen, et al Science (304) 2004

o endothelial cells secrete factors that prevent differentiation of neural stem cells and creates a "neural stem cell niche" that these cells live in.

o These cells are then a pool of dividing cells that differentiate into neurons and glial cells.

Immunology Lectures Review

Cells

1. 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")

o Class I - on virtually all cells, present endogenous antigen to CD8 (killer) T-cells

o Class II - on APCs, present exogenous antigen to CD4 (helper) T-cells

2. Antigen Presenting Cells acquire, process and present antigen

* Dendritic cells, macrophages, B-cells

3. 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

4. Complement cascade

* complement proteins bind to the surface of foreign objects

o direct killing of microbes

o opsinization (for clearance by macrophages

* formation of the MAC

5. 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:

o the variable region determines the specificity of the Ab

o 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

o FUNCTION to secrete antibodies

Concepts:

6. 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

7. Tolerance

o the specificities of the variable regions of the TCR and the BCR (and thus Abs also) are generated in a random fashion

o CENTRAL TOLERANCE self-reactive lymphocytes are DELETED during lymphocyte development

 T cells in the thymus

 B cells in the bone marrow

o 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

8. Hypersensitivity

* consists of an immune response directed against NON-INFECTIOUS agents

o innocuous particles, proteins, etc.

o examples seen in: pollen allergies, food allergies, drug allergies, etc.

o 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:

I) Anaphylactic/IgE-mediated allergic rhinitis, food allergies and systemic anaphylaxis

II) Cytotoxic: mediated by IgG directed against cell- or matrix-associated antigens autoimmune hemolytic anemia, Graves disease, myasthenia gravis

III) Immune complex-mediated - IgG antibodies are directed against soluble antigens, leading to the formation of immune complexes

systemic