Term
| What are the main components of the lymphoid system? |
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Definition
Molecules: Immunoglobulins aka Antibodies
Cells: T & B Lymphocytes
Tissues (Unencapsulated): Nodules & Aggregates
Organs (Encapsulated): Bone Marrow, Thymus, Spleen, Lymph Nodes, Tonsils |
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Term
| What are the basic functions of the lymphoid system? |
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Definition
Antigen Disposal
-Cell-Mediated Immunity
-Humoral Immunity
Immunologic Memory: Second response to same antigen more effective than first
Specificity: Resistance to one antigen does not imply resistance to another.
Tolerance: Distinguishing “self” from “non-self” is key |
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Term
| How does antigen disposal work? |
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Definition
Humoral Immunity
-Mainly B-Lymphocytes
-Activated B-Cells become Plasma Cells
-Plasma Cells secrete immunoglobulins (Ig’s) into tissue fluids (humors)
- Ig's bind to pathogens
Cellular Immunity
-Mainly T-lymphocytes
-Activated T-Cells directly contact and kill invading cells
- T helper cells secrete lymphokines which modulate the immune response |
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Term
| What is the structure of an immunoglobulin? |
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Definition
- there are two heavy chains and two light chains. the heavy chains form the stem and part of each arm of the "Y" structure. The light chains lie in the arms, parallel to the heavy chains
- each chain contains a constant and a variable region. the variable regions in the arm of the "Y" are what cause antibody diversity
- Fc (c for cell binding or crystallization) contains the constant stem regions and this is where the carboxy termini are
-Fab (antigen binding) contains the variable light and heavy chains where antigens bind and this is where the amino termini are
- disulfide bonds connect the light chains to the heavy chains and also the heavy chains to each other |
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Term
| What are the five types of immunoglobulins? |
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Definition
IgM - pentamer
IgA - dimer
IgD - monomer
IgG - monomer
IgE - monomer
mnemonic = MADGE or GAMED |
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Term
| What are the characteristics of IgG? |
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Definition
Most abundant serum Ig
Major Ig in 2ºresponse - the response that occurs after a 2nd exposure to a specific antigen
Greater antigen specificity
Usually a monomer |
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Term
| What are the characteristics of IgM? |
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Definition
2nd most abundant in serum
present on B-cell surface
Major Ig in 1ºresponse - response that occurs after the 1st exposure to a specific antigen
Usually forms pentamers - IgM monomers join by their tails |
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Term
| What are the characteristics of IgA? |
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Definition
Secretory Ig
Mainly in secretions (e.g., mucus, saliva, tears, milk)
Rare in serum
Usually forms dimers
Secretory piece (helical protein) contributed by lining epithelial cells |
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Term
| What are the characteristics of IgE? |
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Definition
Allergic Ig
plays major role in allergic reactions and also parasitic infections
Binds to Fc Receptors on mast Cells & basophils causing release of histamine and heparin causing an inflammatory response
Smooth muscle is relaxed which increased blood flow and characteristics assoc. with inflammation:
- tumor: swelling
- calor: increased temperature
- dolor: pain
- rubor: redness |
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Term
| What are the characteristics of IgD? |
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Definition
primarily on B cell surface
rarely secreted and plasma conc. is very low
Least understood Ig but may function as an embryonic or fetal Ig
Increased levels in children as opposed to adults |
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Term
| What are the three mechanisms of immunoglobulin action? |
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Definition
- Opsonization is where antibodies bind to foreign cells and molecules and make them more likely to be recognized by antigen-disposing cells (macrophages, cytotoxic T cells, neutrophils, eosinophils)
- Neutralization is where antigen-antibody complexes are formed. Antibody binding and cross-linking of antigens into large complexes diminishes or eliminates the toxicity
- The complement system which includes a cascade of reactions which causes
1) inflammation
2) chemotaxis of the inflammatory cells
3) opsonization
4) lysis (components of the system puncture the plasma membrane of the invading cell) |
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Term
| What are the cells of the immune system? |
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Definition
Lymphocytes
-Major effectors of immune response
-T-cells & B-cells
Macrophages
-Phagocytose antigenic material
-Present antigens to lymphocytes
-Enhance recognition
Plasma Cells
-B-lymphocyte derivatives
-Secrete immunoglobulins
Reticular Cells
-Stroma of lymphoid tissues & organs
-Mesenchymal & epithelial types
Other Antigen-Presenting Cells
-Dendritic cells
-Langerhans cells - in the skin
-Kupffer cells - in the liver |
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Term
| What are the basics of lymphocytes? |
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Definition
T- & B-lymphocytes are histologically identical
T- & B-lymphocytes arise from common lymphoid precursor in bone marrow
T-Cell precursor antigen-independent programming occurs in Thymus
B-Cell precursor antigen-independent programming occurs in Bone marrow - different location than where B-lymphocytes arose
T- & B-Cell antigen-dependent programming occurs in secondary lymphoid organs (spleen, lymph nodes,tonsils) & aggregations (e.g., Peyer’s patches, appendix) - this occurs after exposure to a specific antigen |
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Term
| Explain B-lymphocyte differentiation |
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Definition
Programmed as B-cell precursors in Bone Marrow
Programmed as Committed B-cells in Bone Marrow
Programmed to respond to a particular antigen in secondary lymphoid organs
Activated to undergo blast transformation (return to a bigger more embryonic state) and clonal expansion (rapid division) on encounter with antigen
Clonal expansion results in effector and memory cells (about 50% of each) |
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Term
| Explain T-lymphocyte differentiation |
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Definition
Programmed as T-cell precursors in Bone Marrow
Cytotoxic (CD8+) or Helper (CD4+) T-cells in Thymus
Programmed to respond to a particular antigen in secondary lymphoid organs
Activated to undergo blast transformation (revert to a larger embryonic state) and clonal expansion (rapid division) on encounter with antigen
Clonal expansion results in effector and memory cells (can last for years)
Note : The AIDS virus attack T helper cells by binding to CD4 |
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Term
| What are the two types of T-lymphocytes? |
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Definition
Cytotoxic T-Cells
-Carry CD8 antigen on surface
-Activated by antigen complexed with major histocompatability complex class I (MHC-I) molecules
Helper T-Cells
-Carry CD4 antigen on surface
-Activated by antigen complexed with major histocompatability complex class II (MHC-II) molecules
Note - HIV binds to CD4 on Th's |
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Term
| Explain reticular and dendritic cells |
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Definition
Highly branched structure
Exact origin unknown (except that they are mesenchymal)
Present antigen on their surface without phagocytosing it - this causes problems in AIDS. Intact HIV virus is presented on surface so it can infect T helper cells that circulate by
Much longer lived than macrophages, thus assist with immunologic memory. |
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