The Immune System

Words To Know… Pathogen – A disease-causing agent. Histamine – a chemical which causes an inflammatory response. Vascular – Having to do with blood vessels. Antigen – a substance that causes an immune response. Antibody – A defensive protein produced by the body towards a specific antigen.

The Immune System The immune system is a system of cells, structures and processes in an organism that protects against pathogens and diseases.

There are Two immune responses Non-Specific No Target Enemy Specific Specific Target Enemy

First Lines of Defense SKIN Largest organ of body Protects against water loss, chemicals, pathogens Covered in Bacteria and yeasts MUCUS Found inside orifices (holes) Protects against chemicals, pathogens and debris

Non-Specific Response Second line of Defense Inflammation Temperature Proteins White Blood Cells

Second Lines of Defense - Inflammation A biological response by vascular tissues to harmful stimuli: Pathogens Damaged cells Irritants/allergies 4 Cardinal Signs Pain Redness Swelling Heat What causes these 4 signs? Pain – excess blood in the area puts pressure on pain receptors Redness – oxygenated blood in area Swelling – excess blood/fluid in area Heat – carried in by blood

Second Lines of Defense - Fever Temperature (Fever) The process of elevating core temperature in response to a pathogen An elevated tem can inhibit the growth of disease-causing bacteria Can also destroy good cell proteins Fever Ave. temp: 98.6 F Low-Grade:98.6 – 100.4 High-Grade: over 103 F

Second Lines of Defense - Proteins Membrane attack complex (MAC) Various proteins will form a ring on pathogen surfaces, causing them to leak out and die Interferon A protein released by infected cells Causes nearby cells to produce an enzyme that prevents the virus from entering and reproducing.

Second Lines of Defense - WBCs White Blood Cells Cells of the immune system Protect the body against pathogens and foreign bodies

White Blood Cells Neutrophils Most abundant Engulf bacteria, killing it and themselves Natural Killer Cells Largest WBC Best defense against cancer Secretes a cytotoxin that disrupts infected cell membrane Macrophages Means “Big Eater” Eats and kills pathogens and infected cells

White Blood Cells Helper T Cells Activates Cytotoxic T and B cells Cytotoxic T Cell Seeks out ‘labeled’ and infected body cells and destroys them B Cells Labels invaders for future destruction

Specific Response The specific line of defense targets specific pathogens. Those pathogens who have survived the first two rounds now face the Immune Response! 4 Specific WBCs are central to the immune response: Macrophages Helper T Cells Cytotoxic T Cells B Cells

Steps to Immune Response: Virus infects a cell; cell displays viral antigen (red flag) Step 2: Macrophages ‘eat’ virus/cell; they now display same viral antigen Step 3 Receptor proteins on Helper T Cells bind to those viral antigens

Steps to Immune Response: Helper Ts don’t attack, but activate B and Cytotoxic T Cells Step 5 Activated B cells turn into plasma cells and release lots of antibodies Step 6 Antibodies attach to viruses to mark them for destruction

Steps to Immune Response: Antibodies cause viruses and antigens (red flags) to clump together, making it easy for macrophages to find and ‘eat’ them Step 8 Activated Cytotoxic T cells destroy infected cells