Components of the Immune System:

• Lymph, bone marrow, thymus, spleen, leukocytes, antibodies, complement, tonsils and adenoids are among the major components of the immune system.

Antibodies-1:

• IgG is the most abundant antibody in blood.  Only antibody to cross the placenta.
• IgA is the second most abundant antibody in blood. Is the main antibody found in bodily secretions: tears, saliva, mucous, respiratory, intestinal and others.
• IgM third most abundant antibody in the blood and the largest.

Cytokines:

• Interleukins are modifiers of a body’s immune response and modulate inflammation.  They are produced by cells such as lymphocytes, macrophages and monocytes. 
• Growth factors are proteins that are able to stimulate cellular proliferation and differentiation.  They typically act as signaling molecules between cells promoting cell differentiation and maturation. 
• Interferons are a group of proteins which inhibit viral replication in the host’s body.

Hypersensitivity – Type 1:  (Also known as Immediate Hypersensitivity)

• An allergic response due to re-exposure to a specific antigen.
• Is an inflammatory response e.g. asthma, rhinitis.
• Exposure can be a result: ingestion, inhalation, injections or direct contact.
• Mediated by IgE antibodies.
• Results in an immediate release of histamine, tryptase, arachidonate and derivatives by basophils and mast cells.

Hypersensitivity – Type 2: (Also known as Cytotoxic Hypersensitivity)

• Antibody mediated generally by IgG and to a lesser extent IgM.
• Process typically involves K-cells rather than mast cells.
• May involve complement that binds to cell-bound antibodies.
• Antibodies react with “self” antigens.
• Tissue damage may result.
• Antibodies bind to antigens forming complexes that activate the complement for eliminating cells presenting foreign antigens.
• Acute inflammation created at the site were Ag-Ab complexes causing cell lysis and death.
• Example is Erythroblastosis Fetalis the mother produces antibodies that attack the red blood cells of the fetus.  This can occur when the mother and baby have different blood types.

Hypersensitivity – Type 3: (Also known as Immune complex Hypersensitivity)

• Circulating antibodies react with free antigen.
• The complexes can be deposited on tissue which may trigger complement reaction resulting in tissue damage. 
• Aggregations of antigens and IgG and IgM form in the blood.
• The reaction can take hours to days to develop.
• Systemic Lupus Erythematosus is an example of this.  Antinuclear antibodies generate circulating immune complexes that activate complement.  Results in systemic inflammation of body tissues. 

Hypersensitivity – Type 4: (Also known as Delayed Hypersensitivity)

• Cell mediated immune response.
• CD8 cytotoxic T cells and CD4 helper T cells are key molecules involved.
• Antigen presenting cell are macrophages and they release Interleukin 1 stimulating CD4 cell proliferation.
• Activated CD8 cells and macrophages destroy target cells.
• Memory TH1 cells release cytokines that recruit and activate macrophages.
• Examples of this is contact dermatitis i.e. Poison Ivy.

Immunodeficiency Disorders - 1

• Immunodeficiency disorders are a malfunction of the immune system that result in the development and frequent reoccurrence of disease that are also more severe and longer lasting then typical.
• One or more components is defective or missing from the immune system.
• Immunodeficiency disorders can be inherited.
• Temporary immune deficiencies can develop as a function of disease.

Immunodeficiency Disorders - 2

• Depressed immune response due to smoking, stress, surgery transfusions etc.
• Inherited poorly functioning immune system.
• B-cell system not functioning correctly so unable to make antibodies.

Immunodeficiency Disorders - 3

• Thymus missing, small or defective, lacking T-cells.
• Severe Combined Immunodeficiency Disease: birth defect of several immune system organs or defenses.

Autoimmune Diseases: 

• The immune system looses the ability to discriminate between self and other. 
• T-cells and antibodies (called auto-antibodies) are made and directed against “self” cells.  Rheumatoid factor is an auto-antibody. 
• Causes of auto immune diseases include: heredity, infections, certain drugs, sunlight and hormones.
• Type 1 diabetes is caused by the immune system attacking the pancreas cell. 
• AIDS:  The HIV virus attacks and destroys T-cells.  Can also be a latent infection.
• Rheumatoid arthritis:  The body does not distinguish correctly between self and non-self.  The body produces an antibody known as Rheumatoid Factor which is directed against the body’s own immune system.

Definitions:

• Hypersensitivity:  an exaggerated immune response to a foreign agent.
• Inflammation: the first response of the immune system it involves leukocytes entering a site of injury or infection.
• Anaphylaxis:  is a rapid and severe allergic response.
• Auto-immune disease: the failure of the immune system to recognize “self” from other cells.  This results in an immune response against its own cells and tissues.
• Asthma:  is a disease of the respiratory system often resulting from an immune response resulting in inflammation.
• Rheumatoid arthritis is a chronic inflammatory autoimmune disease in which the joints are attacked.
• Mast cells:  contain histamine and heparin and are involve in allergy and anaphylaxis.  They are similar to basophils and granulocytes.
• Cytokines:  peptides and proteins that are used as cell to cell signals. 
• Macrophages

Flash Movie	Flash Game	Flash Card
Core Concept Tutorial	Problem Solving Drill	Review Cheat Sheet

This module outlines the primary functions of the immune system and then details what the major malfunctions in the system are.  The four mechanisms of hypersensitivity and the immune cells and pathways involved in each of the four are described.  Examples of each type and the disease consequences are included.

While the immune system can have hypersensitivity it can also suffer from suppressed immunity which results in a number disease syndromes.  Depressed, suppressed or absent immunity has several disease consequences which are dependent on which immune cells or systems are affected.  Many of these diseases and syndromes are presented.

Specific Tutorial Features:

• Presents the role of the immune system in protecting people from disease.
• Define the different components of the immune system.
• Immunological disorders affecting the correct immune response are described.
• Cells involved in the immune response.

Series Features:

• Concept map showing inter-connections of concepts.
• Definition slides introduce terms as they are needed.
• Examples given throughout to illustrate how the concepts apply.
• A concise summary is given at the conclusion of the tutorial.

Components of the immune system are detailed.
The different antibodies are described: IgG, IgA, IgM, IgE
Cytokines and their function in the body as immune modifiers and cell to cell communication is detailed.
Hypersensitivity – Type 1:  Immediate Hypersensitivity
Hypersensitivity – Type 2: Cytotoxic Hypersensitivity
Hypersensitivity – Type 3: Immune complex Hypersensitivity
Hypersensitivity – Type 4: Delayed Hypersensitivity
Immunodeficiency Disorders - 1
Immunodeficiency Disorders - 2
Immunodeficiency Disorders - 3
Autoimmune Diseases: 
Definitions of significant immunologic terms are detailed.