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 The body has two defense systems for foreign materials that form the immune system  Immunity—specific resistance to disease (such as bacteria, virus, fungus) ◦ Provided for by the adaptive defenses © 2015 Pearson Education, Inc.

 Innate (nonspecific) defense system ◦ Mechanisms protect against a variety of invaders ◦ Responds immediately to protect body from foreign materials  Adaptive (specific) defense system ◦ Specific defense is required for each type of invader © 2015 Pearson Education, Inc.

 mechanical barriers that include: ◦ Body surface coverings ◦ Specialized cells ◦ Chemicals produced by the body  See Table 12.1 for a more detailed summary © 2015 Pearson Education, Inc.

 first line of defense: ◦ Skin and mucous membranes 1.Acidic pH of the skin inhibits bacterial growth 2.Stomach mucosal secretions kill pathogens (HCl) 3.Saliva and lacrimal (eyes) fluid contain lysozyme 4.Mucus traps microogranisms © 2015 Pearson Education, Inc.

 second line of defense: ◦ Natural killer (NK) cells ◦ Inflammatory response ◦ Phagocytes ◦ Antimicrobial proteins ◦ Fever © 2015 Pearson Education, Inc.

 Found in blood and lymph  Release perforin (lytic chemicals) ◦ Does not discriminate ◦ targets abnormal cell’s membrane and nucleus ◦ causes disintegration of cancer or virus-infected cells  animation.html animation.html © 2015 Pearson Education, Inc.

 Takes place when tissues are injured/damaged  Functions: ◦ Prevent spread of damaging agents ◦ Phagocytosis eliminates cell debris and pathogens ◦ Sets the stage for tissue repair  Begins with redness, heat, swelling, pain © 2015 Pearson Education, Inc.

Release of inflammatory chemicals causes: 1. Blood vessels dilate and leak 2. Pain receptors to be activated 3. Influx of neutrophils and macrophages ◦ Neutrophils devour foreign materials ◦ Macrophages replace spent neutrophils and dispose of cell debris © 2015 Pearson Education, Inc.

Neutrophils 1 Enter blood from bone marrow and roll along the vessel wall 2 Diapedesis 3 Positive chemotaxis Capillary wall Endothelium Basement membrane Inflammatory chemicals diffusing from the inflamed site act as chemotactic agents

 Implored when pathogens get through the first line of defense  Macrophages or neutrophils will: 1.Engulf foreign material into a vacuole 2.Vacuole fuses with a lysosome 3.Enzymes from lysosomes digest the material © 2015 Pearson Education, Inc.

(a) A macrophage (purple) uses its cytoplasmic extensions to pull spherical bacteria (green) toward it. Scanning electron micrograph (10,800×).

(b) Events of phagocytosis 1 Lysosome Acid hydrolase enzymes Phagosome (phagocytic vesicle) Phagocyte adheres to pathogens. Phagocyte engulfs the particles, forming a phagosome. Lysosome fuses with the phagocytic vesicle, forming a phagolysosome. Lysosomal enzymes digest the pathogens or debris, leaving a residual body. Exocytosis of the vesicle removes indigestible and residual material Slide 1

 Complement proteins ◦ Complement Fixation: proteins become fixed to sugars/proteins (antibodies) on a foreign cell’s surface ◦ Membrane Attack Complexes (MAC): lesions produced by fixation  Creates holes in the cell’s surface  Water enters and cell bursts © 2015 Pearson Education, Inc.

Antibodies attached to pathogen’s membrane Membrane attack complex forming Pore Activated complement proteins attach to pathogen’s membrane in step-by-step sequence, forming a membrane attack complex (a MAC attack). MAC pores in the membrane lead to fluid flows that cause cell lysis.

 Virus infects cell  Cell secretes proteins called interferons  Interferons bind to receptors on healthy cell surfaces ◦ Interfere with the ability of viruses to replicate DNA ation_quiz_2.html © 2015 Pearson Education, Inc.

 Abnormally high body temperature ◦ Up to 104°-106° - depends on the individual ◦ systemic response to invasion by microorganisms  Regulated by hypothalamus  Inhibits reproduction of bacteria  Increases speed of repair processes © 2015 Pearson Education, Inc.