THE IMMUNE SYSTEM AND MECHANISMS OF DEFENSE Chapter 13

Pathogens can cause damage to our bodies by releasing harmful enzymes or toxins. causing our cells to rupture. using up our body’s resources. d. All the above

Types of Pathogens

Bacteria Characteristics: Prokaryotic Single celled Use of variety of resources for growth and reproduction

Bacterial Infections: Pneumonia tonsillitis tuberculosis botulism syphilis Lyme disease

Viruses Characteristics Extremely small Non-Living?

Viral Infections AIDS hepatitis rabies colds warts chicken pox

Determination of Health Risk Transmissibility: how easily passed from person to person Mode of transmission: respiratory, fecal–oral, body fluids Virulence: how much damage caused by infection

Lymphatic System: Functions Maintenance of blood volume in cardiovascular system Transport of fats and fat-soluble material from digestive system Filtration of foreign material to defend against infection

Lymphatic System: Components protein-containing fluid transported by lymphatic vessels Lymph nodes cleanse lymph by filtering out material Spleen cleanses blood, removes dying red blood cells, helps fight infection

Thymus secretes thymosin and thymopoietin to cause T lymphocytes to mature Tonsils protect throat

SECTION ASSIGNMENT  Due at the end of class USE THE TEXTBOOK

Physical and Chemical Barriers

First Line of Defense Provides physical and chemical barriers: Skin: characteristics of barrier Structure: dead layer, inhospitable to microorganisms Constant replacement: many adhering microorganisms removed pH = 5–6: too acidic for many microorganisms

First Line of Defense Other: tears saliva earwax digestive acids mucus vomiting

Nonspecific Defenses: Second Line

Nonspecific Defenses: Second Line Phagocytosis by neutrophils, macrophages, eosinophils Inflammatory response Signs: redness, warmth, swelling, pain

Inflammatory Response Process: tissue damage leads to release of histamine, blood vessels dilate, complement marks bacteria, phagocytic cells arrive and remove invading microorganisms

The Inflammatory Response Figure 9.7

Lines of Defense: Second Line Natural killer cells: lymphocytes Complement system: group of plasma proteins Interferons: interfere with virus spread Fever: increases host cell defenses and metabolic activity

Cells & Proteins Involved in Specific Defenses

Specific Defense Mechanism: Third Line Immune response Antigens: major histocompatibility complex (MHC) proteins B cells: antibody-mediated immunity, action by antibodies: Classes of antibodies Examples – IgG, IgM, IgA, IgE

Line of Defense: Third Line T cells cell-mediated immunity, action by cells Helper T cells stimulate other immune cells Cytotoxic T cells kill abnormal and foreign cells Memory T cells reactivate on re-exposure Suppressor T cells suppress other immune cells

The Basis of Immunity Due to memory cells

Immune Memory Creates Immunity: Primary Immune Response Process: recognition of antigen, production and proliferation of B and T cells Characteristics: lag time of 3–6 days for antibody production, peak at 10–12 days

Immune Memory Creates Immunity: Secondary Immune Response Process recognition of antigen, production and proliferation of T cells and plasma cells Characteristics lag time in a few hours, peak in days

Medical Assistance in the War Against Pathogens Active immunization effective against viruses Antibiotics effective only against bacteria, resistance a problem

Inappropriate Immune Responses Allergies hypersensitivity reaction, excessive inflammatory response mediated by IgE Types of allergic responses Localized: affect only the area exposed Systemic: affect several organ systems

Anaphylactic shock: severe systemic allergic reaction Symptoms: difficulty breathing severe stomach cramps swelling throughout the body circulatory collapse drop in blood pressure

Inappropriate Immune Responses: Autoimmune Disorders Defective recognition of “self” Lupus erythymatosis (LE or lupus): inflamed connective tissue Rheumatoid arthritis: inflamed synovial membrane