2 The Immune SystemThe body must defend itself against potentially dangerous viruses, bacteria and other pathogens. It must also contend with abnormal cells and cell that may develop into cancer.HIVCancer cells inbone marrow
3 The Immune SystemThere are two types of defense that the body has to fight these threats.Innate Immunity – a defense that is present from birth. Usually nonspecific responding to a broad range of microbes. Consists of external and internal barriers, phagocytic white blood cells called macrophages.Acquired Immunity – also called adaptive immunity. Developes only after exposure to microbes, abnormal body cells, and toxins. Highly specific. White blood cells called lymphocytes are involved as well as proteins called antibodies.
4 Overview of defenses against bacteria viruses and other pathogens INNATE IMMUNITYRapid Responses to abroad range of microbesACQUIRED IMMUNITYSlower responses tospecific microbesExternal defensesInternal defensesSkinMucous membranesSecretions1st line of defensePhagocytic CellsAntimicrobial proteinsInflammatory ResponseNatural Killer Cells2nd line of defenseHumoral Response(antibodies)Cell Mediated response (Cytotoxic lymphocytes)3rd line of defenseFlu Virus
5 External Defenses:These are the first line of defense from diseases
6 Skin is impenetrable to viruses or bacteria. Tiny cuts may allow penetration of pathogens.
7 Mucous membranesline the respiratory, digestive and genitouterary tracts block entry of pathogens. Cells of these membranes produce mucus which traps microbes.Ex: The trachea has ciliated epithelial cells thatsweep mucus and any trapped debris upward away from the lungs.
8 Secretions Saliva, tears - wash away surfaces of epithelial cells. Sebaceous (Oil) glands and sweat glands - give the skin a pH ranging from 3 -5 which is acidic enough to prevent the colonization of some microbesLysozyme – an enzyme contained in secretions from the skin that digests the cell walls of many bacteria (peptidoglycan)Gastric Juices – acidic pH kills pathogens before they reach the intestines.Exception: Hepatitis A virus can survive gastric acidity
9 Internal Defenses – 2nd Line microbes that get past the external defenses must then contend with the internal mechanisms of innate defense.
10 Phagocytic Cellsphagocytosis is the ingestion of invading microorganisms by a certain type of wbc called phagocytes.Phagocyte andgonococci
11 Attach to their prey by way of surface receptors that bind to structures found on many microbes but not on regular body cells. An example of this structure is polysaccharides found on the surface of bacteria.Engulfs the microbe(s) then forms a vacuole.Vacuole fuses with a lysosomeNitric oxide and other toxins poison the microbesEnzymes breakdown the molecules that make up the microbe
12 4 Types of White Blood Cells (leukocytes) that are phagocytic: NeutrophilsEnter infected tissue and engulf microbes about 70% of wbc’s. Self destruct in a few daysMacrophages“the big eater” large phagocytes thatengulf microbes anddead tissue cells. Live longer than neutrophils
13 Eosinophils Dendritic Cells Attack large parasites with enzymes (blood fluke)Dendritic CellsIngest microbes like macrophages and stimulates acquired immunity
14 Antimicrobial proteins – proteins that become activated and secreted when there is an infection. Examples include lactoferrin binds iron which is necessary for bacteria to grow and defensins which kill fungibacteria and viruses
15 Complement System - a group of proteins that lead to the lyses (bursting) of invading microbes. Substances on the surface of microbes activate the complement system.
16 InterferonsLimit the spread of viruses by keeping them from replicating.
17 Inflammatory Response Damage to tissue by physical injury or entry of pthogens leads to the release of chemical signals that trigger a response.Histamine - a chemical stored in mast cells found in connective tissues. Histamine dilates capillaries and increases their permeability
18 Chemokines are small proteins that guide phagocytes to the site of injury Macrophages release chemicals like prostoglandins that promote blood flow to the site of injuryResult is inflammation, redness, swelling.
19 Natural Killer CellsNK cells patrol the body and attack viral infected cells and cancer cellsOnce attached to an infected cell, it releases chemicals that cause the cell to undergo apoptosis (programmed cell death)NK cells are not 100%effective.