The Immune System Tucker, Kathy, Hunter, Brielle

Functions ●Scavenge dead or dying body cells ●Destroy abnormal/cancerous cells ●Protect from foreign molecules (bacteria, viruses)

3 Lines of Defense Chemical and physical barriers Nonspecific Resistance Specific Resistance

Physical Barriers First line of defense ○ Skin: thick layer of dead cells ○ Mucous membranes that trap microbes ○ Hair in the nose that traps dust and pollutants ○ Cilia: small hairs that trap pollutants ○ Urine ○ Vomiting (Allied health)

Chemical Barriers First line of defense ●Antibiotic lysozyme enzyme: in tears and sweat ●Gastric juice--acidity destroys bacteria and toxins ●Saliva washes mouth and teeth ●Acid on the surface of the skin ●Sebum: oily secretion of glands ●Hyaluronic acid: viscous fluid (Allied Health)

Nonspecific Resistance Second line of defense: destroys invaders in a generalized way that does not target specific individuals ●Inflammation brings more white blood cells to site where microbes have invaded ●Fever inhibits bacterial growth ●Phagocytic/macrophage (cells) destroy microbes that pass into body tissues ○Phagocyte attaches to microbe ○Phagocytes plasma membrane surrounds microbe and takes it into the cell in a vesicle ○Vesicle merges with a lysosome ○Digestive enzymes break down microbe --> phagocyte uses microbe’s nutrients ○Phagocyte produces protein markers that enter the vesicle ○Indigestible material is removed in exocytosis ○Antigenic fragments bind to protein markers and are displayed on plasma membrane surface ○Phagocyte secretes interleukin 1

Phagocyte destroying Microbe

Overview

Specific Resistance Third line of defense: when nonspecific methods are not enough and infection becomes widespread ●Steps for an immune response using lymphocytes (helper T-cells): ○When an antigen is detected by a macrophage (nonspecific resistance), the interleukin 1 activates helper T-cells ○The body has millions of different helper T-cells all able to respond to one specific antigen... similar to enzymes and specificity! ○Helper T-cells bind to the marker proteins and secrete interleukin 2 which causes the cytotoxic T-cells and B-cells to be made rapidly ○From here, the response can take 2 paths: one with cytotoxic T-cells and the other with B-cells … (Starr, Taggart)

Cytotoxic T-cells Involved in third line of defense ○The “killer” cell ○T-cell function: to destroy the pathogen in the infected body and tumor cells ○T-cells arise from stem cells in the bone marrow ○T-cells recognize antigens on surface of infected body cells ○Bind to infected surface and secrete cytotoxins that induce apoptosis (cell suicide) and perforins that cause punctures and holes in the infected cells ○This is called cell-mediated immunity (Nobel Prize)

B-cells Involved in third line of defense (B-cell pathway) ○Helper T-cells stimulate B-cells to divide, forming plasma cells that produce antibodies and memory B-cells ○If the same antigen enters the body again, the memory B-cells react quickly by making more specific antibodies to fight against the recognized attack ○The antibodies circulate through the bloodstream and bind to specific antigens, attacking and killing the present microbe ○This is called antibody-mediated immunity (Nobel Prize)

Entire Process antibody-mediated immunity

Fun Facts The term "antigen" comes from ANTI-body GENerating substances (Allied Health) ●Getting under 5 hours of sleep a night depresses your immune system ●People who lack humor in their lives tend to have less protective immune responses ●In your blood, there are around 50 billion white blood cells ●Dieting decreases natural killer cell functionality, therefore weakening the immune system. ●While the body needs some sunlight to produce vitamin D, too much sunshine can suppress the immune system (Sisson)

Recap

Definitions White Blood Cell: any of the various blood cells that help prevent disease Phagocyte/macrophage: a cell that engulfs and consumes foreign organisms Cytotoxic T-Cells: white blood cell known as “killer cell” B-Cells: white blood cell that produces antibodies Helper T-Cells/lymphocytes: T-cell that controls the activity of other white blood cells Pathogen/microbe: bacteria, virus or other microorganism that causes disease Antigen: a toxin that induces an immune response in the body Antibody: a blood protein that counteracts a specific antigen Interleukin 1 and 2: secreted proteins in an immune response

References Allied Health Educational Grant Program. "Immune System." Associate Degree Nursing Physiology Review. Ed. Austin Community College. N.p., Aug Web. 30 Oct atoryresponse.html#top "The Immune System - in More Detail". Nobelprize.org. Nobel Media AB Web. 31 Oct < -detail.html-detail.html> National Institutes of Health. "Immune System." National Institute for Allergy and Infectious Disease. Ed. U.S. Department of Health and Human Services. U.S. Department of Health and Human Services, 23 Oct Web. 30 Oct Sisson, Mark. "10 Things You (Likely) Don’t Know About Your Immune System." Marks Daily Apple. 19 Aug Nov < likely-dont-know-about-your-immune-system/likely-dont-know-about-your-immune-system/>. Starr, Cecie, and Ralph Taggart. "Immunity." Biology: The Unity and Diversity of Life. Pacific Grove: Jack c. Cary, Print.