A. The skin and mucous membrans: The skin and mucous membrans act as a physical barrier preventing entry of pathogens, and as chemical barriers of anti pathogens secretions
1. Oil and Sweat lower pH (3-5) [acidic, H+]
2. Helpful bacteria on skin
3. Lysozyme in tears, saliva + sweat attack cell walls of bacteria
4. Mucous traps dirt, microbes etc. Cilia sweeps them out
5. Stomach acids kill bacteria
II. Second line of defense: Non-specific
A. Phagocytic White Cells and Natural Killer Cells: Microbes taht penetrate the skin encounter amoeboid white blood cells capable of phagocytosis of cell lysis.
1. Neutrophils are cells that beocme phagocytic in infected tissue.
a. 60-70% WBC.
b. Ameoboid movement/ destroy themselves when destroying pathogens ("Kamakazis")
2. Macrophages are large amoeboid cells tha tuse pseudopodia to phagocytize microbes that are destroyed by digestive enzymes and reactive forms of oxygen within the cell.
a. Most wander in interstitial fluid phagocytising pathogens + cell debris.
b. Some reside permanently in organs and connective tissue
c. Circulate in blood & lymph vessels
d. Develop from monocytes. 5% WBC
3. Eosinophils represent abou 1.5% of the total white cell count but have limited phagocytic activity.
a. contain destructive enzymes in cytoplasm and release them via exocytosis.
b. Helps to destroy larger invaders such as parasitic worms
4. Natural killer cells destroy the body's own infected cells esp. those harborng viruses.
a. Assault cells that could form tumors
b. Not phagocytic: attach memebranes to cell lysis.
B. Antimicrobial Proteins: A number of proteins in nonspecific defense by either directly attacking microorganisms or impeding thier reproduction.
1. The two most important nonspecific protein groups are complement and the interferons.
a. Complement - a gorup of at least 20 proteins which interact w/other defense mechanisms.
b. Interferons - Substances produced by virus infected cells which help other cells resist infection by the virus.
C. Inflammation : the inflammatory response occurs when there is damage to a tissue due to physical injury of entry of microorganisms.
1. Swelling.
2. Increase blood flow & lympth flow
3. Increase temp. (fever)
4. Increase # of WBC to fight infection + repeair damaged tissues.
*Chemical signals are important for initiating hte inflammatory response.
*Migration of phagocytic cells into the injured area is also a result of increased blood flow and increased leakage for the capillaries.
*More widespread (systemic) inflammatory response may also occur in cases of sever infections.
III. Third line of defense: specific
Distinguished by nonspecific defese by: specificity, diversity, self/nonself recogniciton, and memory.
*Specificity - immune system's ability to recognize specific antigens
*Antigen - anything that causes an immune response
*Antibody - Protein that works to destroy antigens
*Diversity - the immune system's ability to respond to numerous kinds of invaders which are recognized by thier antigenic markers.
*Self/nonself - recognition is the ability fo the immune system to distinguish b/w the body's own molecules and foreign molecules.
*Memory - the immune system's ability to recognize previously encountered antigens and to react faster and more effectively to subsequest exposures.
