1. Blood: The White Blood cell

2. Review: One of the 4 main components of the blood = white blood cells (leukocytes) White blood cells are a major component of your immune system There are many types of WBC’s (macrophages, T cells, B cells, basophils, etc.) Your immune system helps to protect your body from invaders (bacteria, viruses, etc.)

3. Challenges for the immune system: Constant surveillance and vigilance Unpredictable invaders

4. The Enemy Pathogens: microorganisms that are capable of causing disease. An antigen is anything that causes an immune response 1. Viruses 2. Bacteria 3. Fungi (Remember:. Pathogens carry antigens on their surface but not all antigens are produced by pathogens. Allergies are caused by the immune system mistaking antigens present on nonpathogenic substances or organisms for those of pathogens.)

5. Public Enemy #1: The Viruses What they do: 1.The virus docks with receptors on target (human) cell surface 2.Insert viral DNA or RNA into host cell 3.Use host cell machinery to replicate many new viruses 4.Lyse (kill) host cell and spread to nearby cells Lytic vs. Lysogenic life cycles Examples: smallpox, chickenpox, polio, HIV, influenza, SARS

6. Smallpox

7. Public Enemy #2: Bacteria What they do: 1.Live in tissues but remain EXTERNAL to human cells 2.Reproduce rapidly 3.Secrete exotoxins or contain endotoxins as part of cell wall Examples: Escherichia coli, Clostridium botulinum, Salmonella, Streptococcus Figure from Holt Biosources

8. Description: Necrotizing fasciitis, commonly known as Flesh Eating Bacteria (decaying flesh) is a form of infection generally caused by group A streptococcus, a variant of the same bug that causes strep throat

9. Public Enemy #3: Fungi What they do: 1.Similar to bacteria- reproduce rapidly 2.Damage cells directly or indirectly by secreting digestive enzymes. (They want to eat you!) 3.Also produce toxins. Their purpose is to keep down the competition – bacteria. Examples: Athlete’s Foot, Pneumocystis carinii (fungal pneumonia)

10. So what’s a body to do? First line defenses: physical barriers 2 nd line of defense: Inflammation

11. So what’s a body to do? First line defenses: physical barriers – skin: a layer of dead tissue that forms an impenetrable barrier –Saliva & tears: contain an enzyme (lysozyme) that destroys bacteria & viruses –Mucus: in the lining of the respiratory system catches pathogens. Cilia move the mucus up and out of the RS. –Stomach acid: destroys pathogens that are swallowed. –Fever: raises body temperature higher than pathogens’ ideal and speeds up metabolic rate. Faster metabolic rate accelerates immune response.

12. Inflammatory Response 1.At the first sign of injury/invader, nearby cells and basophils passing by the site of an infection release a chemical called histamine 2.Histamine causes a dilation of capillaries and an increase in capillary permeability. This allows more blood into the area and more WBCs out into the infected tissues where they can battle pathogens 3.WBCs battle with pathogen by phagocytosis and releasing chemical to damage and mark pathogens 4. This all results in “inflammation” - redness and swelling

14. What about when the body attacks itself? Autoimmune diseases: When the immune system mistakes self tissues for non-self (like a pathogen) and mounts an inappropriate attack. Examples: Wegener's granulomatosis, multiple sclerosis, type 1 diabetes mellitus, rheumatoid arthritis, lupus Multiple sclerosis (MS)