The immune system

List the most common pathogens and give examples for each

Bacteria - Leprosy

Fungi - tinea (athletes foot)

Protozoa - Plasmodia (malaria)

Parasites - Helminths (Tapeworm)

Virus - HIV (aids)

Prion - CJD

Name and describe the functions for the lymphatic organs

Spleen - Filters old red blood cells and helps fight infection. Has red pulp which cleans blood and stores it, and white pulp which has immune cells that scans for germs.

Thymus - Thymus gland is the site of maturation of T cells. Secretes 2 hormones that control T-cell development - thymosin and thymopoietin.

Tonsils - filter food and protect the throat

Adenoids - filter air and back of nasal passages

What is the body’s first line of defense?

The skin. Can expel pathogens through tears, saliva, earwax, mucus, vomiting, urination

Explain the non-specific defense mechanisms when pathogens get past the skin

Complement proteins - Plasma proteins that invade bacteria when activated. Activated complement proteins form protein complexes that create holes in bacterial cell wall. Water and salts diffuse into the bacterium. The bacterium bursts.

Phagocytic cells - White blood cells that surround and engulf invading bacteria. Neutrophils: first responders. Macrophages: leave blood and enter tissues. Eosinophils: large parasites.

Inflammation - Redness, warmth, swelling, pain. Damaged cells and mast cells in the area release histamine which dilates blood vessels. Complement bacteria diffuse out and mark the bacteria for destruction. Attracted by histamine, phagocytes begin attacking bacteria and debris.

Explain the roles of B and T cells in the body’s specific defense mechanisms

B-cells : Antibody mediated immunity - B-cells makes antibodies that bind with and neutralize specific antigens. Active against viruses, bacteria and soluble foreign molecules.

T-cells : Cell mediated immunity - Directly attack foreign cells, co-ordinates immune response, active against viruses, parasites, fungi, cancer cells.

Describe 3 types of T-cells

Helper T cells (CD4) stimulate other immune cells

Cytotoxic immune cells (CD8) kill abnormal and foreign cells

Memory T cells reactivate during later exposure

Differentiate between a primary and secondary immune response

Primary: occurs on first exposure to antigen, lag time of 3-6 days for antibody production, peaks at 10-12 days

Secondary: Occurs on second exposure to antigen. Lag time is hours, peaks in days and much more antibody produced.

Analyze why organ transplant patients need immunosuppressive drugs

Tissue rejection can occur if recipients immune system attacks the transplanted tissue/organ. Immunosuppressive drugs prevent patients immune system from attacking transplanted tissue.

Indicate the difference between allergy and autoimmune responses

Allergy - involve over-reaction to harmless external substances known as allergens.

Autoimmune - Involve the immune system attacking the body’s own healthy tissues.