Immune System

1. Immune System

2. Two nonspecific defense systems • First line of defense • Skin and mucous membranes • Second line of defense • Nonspecific cellular and chemical protection devices • (Third line of defense = specific immune responses to kill particular organisms)

3. First line of defenseSkin and mucous membranes • Skin has 4 ways to block entry of disease • Structure • Dead, dried out keratinized cells – waterproof barrier • Continuously replaced – • pathogens get sloughed off • Acidic • pH 5-6 is hostile environment • Sweat glands produce antibodies • Dermicidin kills a wide range of harmful bacteria

4. Mucus and other secretions • Tears, saliva, earwax • Tears & saliva contain lysozyme = bacteria killer • Earwax traps particles • Mucus secreted in GI tract, respiratory tract mires microorganisms • Cilia beat constantly and sweep away pathogens (coughed up or swallowed)

5. Mucus and other secretions cont’d • Digestive and vaginal acids – low pH hostile environment • Vomiting, urination, defecation all remove microorganisms • Urine is acidic • Vomiting cleans the stomach • Diarrhea speeds pathogen expulsion

6. Nonspecific cellular and chemical defense • White blood cell army are Generalists – attack everything, clean up & repair crew • Phagocystosis – captures and digests • Neutrophils – first to respond, digest, destroy • Macrophages – engulf and digest large numbers of invaders • Eosinophils – cluster around large parasites and bombard with digestive enzymes

7. Inflammatory Response • Warmth, swelling and pain • Starts when tissue is damaged • Chemical stimulus calls mast cells to release histamine • Histamine capillaries  permeable  phagocytes to enter battle along with more blood • Extra fluid dilutes pathogens and toxins & brings in clotting proteins to wall off damaged area • Extra oxygen & nutrients promote tissue healing & carries away damaged cells, microorganisms & debris • Swollen tissue press on nerves causing pain  reduces movement

8. Adaptive (specific) defense system • Works in conjunction with the intrinsic: • it identifies the specific invader, • participates in the specific invader's destruction by either • killing them directly • activating the inflammatory response • activating complement proteins • making antibodies

9. Lymphocytes role • T cells participate in adaptive cellular defense (kill or help with the kill) • B cells make antibodies that help with the destruction of the invader

10. B-cell immune response. • Antibody mediated immunity • B cells (bone marrow) move to lymphatic tissues and become plasma cells (cells transported by the plasma) that produce antibodies (antibodies are proteins capable of inactivating antigens) • B cells must be activated by helper T cells • Antibodies are secreted into the blood, lymph and mucus – they combine with the antigen and mark them for destruction

12. B cell immune response cont’d • Once antibody production is enough to cause the antigen to disappear the development of the plasma cells stops • Some cells remain (memory B cells) in case of future invasion = active immunity

13. What is active immunity? How can it be acquired? • Occurs when b cells encounter antigens and produce antibodies • Artificially acquired – vaccine • Naturally acquired – natural contact

14. What is passive immunity? How do you get it? • Antibodies are obtained from the serum of an immune person • B cells do not produce new antibodies (there is no antigen challenge) – so no memory cells are made • Protection ends when donor antibodies degrade – but search and destroy while present • Mother to fetus, breast feeding • Snake bite serum, rabies shots