Think, think, think…. What is a pathogen?

Infection is… The presence and multiplication of a disease causing agent – a pathogen Pathogens include: Viruses Bacteria Fungi Protozoan

Nonspecific defense vs Specific defense What is the difference?

Nonspecific Defense General protection against many types of pathogens Types include: 1st layer of defense Species resistant Mechanical barriers 2nd layer of defense Chemical barriers Fever Inflammation Phagocytosis

Species resistant Development of a species specific set of diseases that only affect that species. For example: Measles, mumps, gonorrhea, and syphilis ONLY affect humans and no other species of animal. (Remember that a species is defined as an individual that can only mate with another individual of its kind and can produce offspring)

Mechanical barriers Skin, skins accessory organs, and membranes that line the outside and inside of the body provide a defense against pathogens entering into the body. First line of defense Example: hair traps infectious agents, and body fluids rinse away microorganisms.

Chemical barriers Enzymes in the body are a chemical barrier to pathogens. Enzymes and other fluids in the body have a certain pH which is lethal to many pathogens entering the stomach. Tears are antibacterial. Salt from perspiration kills bacteria on skin. Lymphocytes and fibroblasts chemically respond to viruses or tumors.

Fever Elevated body temperature reduces the level of iron in the blood. Iron is needed for bacteria and fungi to survive in high temperatures. Growth of bacteria and fungi is reduced. Phagocyctic cells attack more when temperature rises.

Inflammation Tissue response to injury and infection = localized redness, swelling, heat, and pain Inflammation walls off the site of infection so that the infection cannot spread throughout the body. The increase in blood and fluids to the area brings phagocyctic cells and clotting factors to the area – keeping the infection contained.

Phagocytosis Neutrophils and monocytes Neutrophils engulf and digest down smaller particles Monocytes engulf and digest larger particles Phagocytosis removes foreign particles from the lymph; phagocytes in the blood stream and tissues remove particles from the spleen, liver, or bone marrow. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__phagocytosis.html

Specific Defenses 3rd line of defense Immunity Antigens Lymphocyte origin

Antigens Proteins, polysaccherides, glycoproteins, and glycolipids are found on the cell’s surface = antigen During fetal development the lymphatic system begins to recognize “self” cells and tissue and responds to the “nonself” (foreign antigens) cells and tissues Receptors on lymphocyte help the cell to recognize foreign antigens.

Antigens Most effect responses are large and complex. Smaller molecules can get into the body and are so small they cannot elicit a response. Small molecule = hapten Hapten can be found in penicillin, household and industrial chemicals, dust, and animal dander. What is it called when you have a reaction to hapten?

Lymphocyte origins During fetal development bone marrow releases undifferentiated cells that end up in the thymus while others remain in the bone marrow. Lymphocytes in thymus gland = T cells Lymphocytes in the bone marrow = B cells T cells comprise about 70-80% of the circulating lymphocytes in the blood B cells comprise about 20-30% of the circulating lymphocytes in the blood

T cells Attach to foreign antigen-bearing cells, such as bacteria Direct cell-to-cell interaction May secrete a toxin to kill the foreign antigen Create memory cells two types of T-cells: helper and cytotoxic

T cells Helper T-cells: specialized type of cell which contacts a foreign antigen and stimulates B-cell to produce antibodies Cytotoxic T-cells: recognizes nonself antigens (cancers or viruses) and is activated and destroys the cell http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter22/animation__t-cell_dependent_antigens__quiz_1_.html http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter22/animation__t-cell_dependent_antigens__quiz_2_.html

B-cells Produce anitbodies or immunoglobulins Differentiate into plasma cells Carried by body fluids and react in different ways to destroy specific antigens or antigen-bearing particles Create memory cells which respond rapidly to a specific antigen Other B-cells differentiate into plasma cells which secrete antibodies http://www.youtube.com/watch?v=iDYL4x1Q6uU

Your assignment: Check your recall pp Your assignment: Check your recall pp. 374, 376, 377, 380 (only under immune response) p. 389 review exercises 8, 9, 12, 14, 15, 16, 21, 23,