Germ Theory ofDisease• “Microorganisms cause infectiousdisease”• Louis Pasteur and Robert Koch did severalexperiments to identify disease causingagents.• Determined that each disease is causedby a “specific” microorganism
Agents of Disease• The following types oforganisms can causedisease:1. Viruses2. Bacteria3. Protists (malaria)4. Worms5. Fungi• Pathogen is anythingthat causes disease.
Koch’s Postulates• In order to identify what organism causes a specificdisease, certain rules are followed.• Koch Postulates:1) pathogen must be found in subject with diseasebut never in a healthy subject2) pathogen can be isolated from sick person andgrown in lab3) pathogens injected into healthy person willcause the individual to become infected with thesame disease4) injected pathogens can be isolated from newlyinfected individual and are identical to originalpathogens
Koch’s Experiment- GermTheory• Koch’s postulates are very important becausethey are the basic steps for identifying, curing,and preventing specific diseases.
What is a system?• A group of tissues (organs) work togetherto do a task.• Ex) digestive system, circulatory system,immune system…• Function of the immune system is toprotect body from invasion by pathogens.
Overview of Body’sDefensesNon-Specific Defenses Specific DefensesFirst Line of Defense Second Line ofDefenseImmune ResponseSkin and Mucous InflammatoryResponseNon-SpecificWBC (phagocytes)Specific (diverse)Antigens/AntibodiesLots WBCMemory
Non-Specific Defense• Similar to “walls of a fort” protect by keepingpathogens out of body• Body does NOT distinguish one pathogen fromanother• Your body has several non-specific defenses…1) External- skin and mucous membranes(1stline defense)2) Internal- Inflammatory response(2ndline defense)
“Skin”• Physical barrier• Chemical barrier-secretes oil andsweat (lowers pHskin), tears (containenzyme calledlysozyme), and saliva• Sheds constantly(1 million cells perhour)
“Mucous Membranes”• Skin contains naturalopenings (nose, mouth,trachea, esophagus)• These areas are lined bymucous membranes• Secrete mucus trapsforeign objects• Areas lined with cilia• Any pathogens make itpast, may be killed bystomach acids.
“Small ScaleInfections”• The first line of defense has been broken… second line of defenseis triggered to attack any invaders present• Inflammatory response• Body’s attempt to destroy pathogens that enter the body whenthe skin is injured• Triggers series of reactions …1.) Chemical called histamine is released from white bloodcells called basophils2) Blood vessels in area of injury swell3) Tissue at injury site swells4) Temperature in area of injury rises = redness5) White blood cells called phagocytes move from the vesselsinto the injured tissue eat pathogen and damaged skin cells6) Platelets clot blood and seal infected area
“What if pathogens getin?”• White blood cells take over and specifically identify andeliminate the pathogen.• White blood cells = “soldiers”• Immune Response
Organs of the ImmuneSystemWhite blood cellscalled leukocytesMade thymus andbone marrowStored tonsils,spleen, and lymphnodes.
How does your bodyknowthere is an invader?• All pathogens have “distinct” antigens.• Antigens are marker proteins- trigger immuneresponse• Your body must recognize antigens in order toidentify and defeat the pathogen.• Normal cells also have antigens.Antigen
Antibodies• Your white blood cells produce antibodies inresponse to specific antigens.• These are specific to each pathogen.• All pathogens are unique, your immune systemhas to prepare a specific defense against eachinvader.• If you makes/have the antibodies it can kill thepathogen and you can fight the infection.• B-cells (type of white blood cell) make theantibodies!
Building “Immunity”• What happens if a pathogen makes itpast the first lines of defense and avoidsthe inflammation response?• Your body must “actively” fight thedisease.• This takes time.• This requires a special group of whiteblood cells lymphocytes.
“The Soldiers”• Many types of WBCwork together duringthe immune response tofight the infection.• Macrophages• Lymphocytes
“The Soldiers”• 3 major classes oflymphocytes:1) B-cells (plasma cells)2) T-cells-Helper T cells-Killer T cells-Suppressor T cells3) Memory cells
Step #1 “InvaderIdentification”• Macrophages identify pathogen, eat it, displayantigens, signal helper T cells (interleukin-1).• Body temperature will increase (interleukin-1) inattempt to slow down pathogen.
• Helper T cells release interleukin 2 – signalshelp other leukocytes (other T-cells and B-cells)
Step #2 “CloningPhase”• B cells make antibodies - lock ontoantigens.“Marked for death.”AntibodiesAntigen
• Killer T cells kill infected body cells.Step #3 “The Attack Phase”
Step #3 “The AttackPhase”• Macrophages clean up- eating pathogens,damaged body cells, etc.• Suppressor T cells “call off the troops” stoppingthe immune response.
Step #4 “MemoryPhase”• Memory cells “remember” the attack andrecognize a pathogen if it re-enters body.• Primary vs. secondary immune response
Active vs. PassiveImmunity• Active = your body must fight off thedisease to build up antibodies. Ex.)Fighting an infection or Vaccination• Passive = receiving antibodies from anoutside source. Ex.) Breast feeding
Other Topics – Relatedto Immune System•It is the job of the immune system todistinguish between the body’s ownmolecules and foreign molecules•Antigens – “marker proteins”•Blood Transfusions and Organ Transplants
If the key fits the lock = bad!!!Blood Transfusions and the ImmuneSystem• Blood cells have marker proteins or“antigens”
Organ Transplants and theImmune System• Foreign organs also have markerproteins.• If recognized as “foreign” = REJECTION.• Doctors must “match” a new organsmarker proteins to the patients.• Drugs can help suppress the immuneresponse (immunosuppresants).
What if the immunesystem fails?• Sometimes the immune system loses theability to distinguish itself from non-self.• Results in autoimmune disease• Body attacks own tissues• Ex) lupus, multiple sclerosis, arthritis
LUPUS• Person’s immune system attacks variousorgans or cells of the body (skin, joints,kidneys, heart, and lungs) causingdamage• Lupus is a multi-system disease becauseit can affect many different tissues andorgans in the body.
LUPUSSymptoms:• Fatigue• Low-grade fever, rarely exceeding 102°F• Muscle pain and joint pain or swelling• Skin rash (face, back, arms) and hair loss• Kidney problems and weight loss
MultipleSclerosis• Immune systemattacks myleinaround nerve cells• Symptoms: loss ability to walk and move,loss bladder control, paralysis and death
What if the immunesystem fails?• Sometimes the immune system collapses• Ex) HIV• Virus invades macrophages and helper Tcells• Without these WBC immune responsewill not work• Body becomes overwhelmed withpathogens (HIV AIDS)
AIDS (Acquired ImmuneDeficiency Syndrome)• Retrovirus (has RNA instead of DNA).• Lysogenic (stays dormant for a longperiod of time).• Easily evades immune system.1. Mutates quickly.2. Covers itself with marker proteins fromhost cell (difficult to detect).
Transmission of HIV• Four main ways1. Sexual intercourse.2. Intravenous drug use (sharing needles)3. Blood to blood contact4. Mother to child during pregnancy orbreast feeding.
What if the immunesystem fails?• Sometimes the immunesystem overreactsthinking something is apathogen when it is NOT• Allergy- immune systemresponse to a non-pathogenic antigen• Ex) pollen, food, insectbite, dust, etc.
Steps – AllergicReaction• 1) Pollen inhaled• 2) cells of nasalpassage called mastcells release chemical-histamine• 3) nearby capillariesswell- increases fluid*Allergies are treatedwith medication thatcontainsantihistamines(chemical that blockshistamine)
Immune System andCancer• Major function of immune system is topatrol for cancer cells• Called Immunological Surveillance• Killer-T cells can identify, attack, anddestroy cancer cells