Presentation on theme: "THE IMMUNE STYSTEM. The Immune System The body must defend itself against potentially dangerous viruses, bacteria and other pathogens. It must also."— Presentation transcript:
THE IMMUNE STYSTEM
The Immune System The 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. Cancer cells in bone marrow HIV
The Immune System There 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.
Overview of defenses against bacteria viruses and other pathogens INNATE IMMUNITY Rapid Responses to a broad range of microbes ACQUIRED IMMUNITY Slower responses to specific microbes External defensesInternal defenses Skin Mucous membranes Secretions 1 st line of defense Phagocytic Cells Antimicrobial proteins Inflammatory Response Natural Killer Cells 2 nd line of defense Humoral Response (antibodies) Cell Mediated response (Cytotoxic lymphocytes) 3 rd line of defense Flu Virus
External Defenses: These are the first line of defense from diseases
Skin is impenetrable to viruses or bacteria. Tiny cuts may allow penetration of pathogens.
Mucous membranes line 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 that sweep mucus and any trapped debris upward away from the lungs.
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 microbes Lysozyme – 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
Internal Defenses – 2 nd Line microbes that get past the external defenses must then contend with the internal mechanisms of innate defense.
Phagocytic Cells phagocytosis is the ingestion of invading microorganisms by a certain type of wbc called phagocytes. Phagocyte and gonococci
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 lysosome Nitric oxide and other toxins poison the microbes Enzymes breakdown the molecules that make up the microbe
4 Types of White Blood Cells (leukocytes) that are phagocytic: Neutrophils Enter infected tissue and engulf microbes about 70% of wbc’s. Self destruct in a few days Macrophages “the big eater” large phagocytes that engulf microbes and dead tissue cells. Live longer than neutrophils
Eosinophils Attack large parasites with enzymes (blood fluke) Dendritic Cells Ingest microbes like macrophages and stimulates acquired immunity
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 fungi bacteria and viruses
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.
Interferons Limit the spread of viruses by keeping them from replicating.
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
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 injury Result is inflammation, redness, swelling.
Natural Killer Cells NK cells patrol the body and attack viral infected cells and cancer cells Once attached to an infected cell, it releases chemicals that cause the cell to undergo apoptosis (programmed cell death) NK cells are not 100% effective.