1. IMMUNE SYSTEM
CHAPTER 48

2. I) Immune System Components
Antigens
Any substance that causes an immune response
Protein receptors on cells
Proteins on outer surface of pollen
Dust
Various chemical compounds (toxins, secretions, proteins)
Pathogen
Disease causing antigen
Bacteria, virus, toxin
Antibodies
Proteins produced by B-Lymphocytes that chemically interact with antigens
Results in specific recognition of antigens

3. II) Lines of Defense First Lines of Defense – Nonspecific Response
Broad spectrum “barriers” to infection
Skin
Waterproof covering
Sebaceous oil – lowers pH of skin to retard bacterial growth
Mucous Membranes - secrete mucus
Located in digestive, respiratory and urogenital tracts
Contain lysozyme – antimicrobial enzyme
Tears, saliva, urinary and reproductive tract secretions
Stomach acid destroys most bacteria and virus

4. II) Lines of Defense Second Lines of Defense – Non-Specific Response
Non-specific attack of foreign antigens
Macrophages attack and ingest foreign entities
Complement proteins form complexes to perforate foreign cells
Bind to membranes and cause lysis of cells
Inflammation is swelling of tissues due to histamine secretion
Increased blood flow and white cell activity to an affected area
Dilation of blood vessels in local area
Pyrogens – proteins that increase temperature (fever)
Stimulate white cell activity
Promotes phagocytosis
May help to attenuate (slow) bacterial proteins
Symptoms of
Infection

5. II) Lines of Defense Specific Defenses
B cells (B lymphocytes) respond to antigens by producing antibodies that provide humoral immunity
Memory cells retain the “imprint” of the antigen for future infections
Provide a rapid response to future infections
Plasma cells rapidly secrete antibodies in response to a specific antigen
T cells (T lymphocytes) have multiple functions that provide a cell mediated response
Helper T-Cells: Regulate the immune response of other cells
Killer (Cytotoxic) T-Cells: Directly attack cells carrying specific antigens
Killer T-Cells need information about the antigen communicated by the Helper T- Cell

6. III) The Specific Immune Response
Cell Mediated Response
Macrophages engulf antigens and express components on the plasma membrane
This is an antigen presenting cell (APC)
Helper T-Cells recognize the antigen presenting cell and become activated
Helper T-cells secret interleukins to stimulate Killer T-Cells (Cytotoxic)
Interleukin communicates the antigen information to the cytotoxic T- Cells
Cytotoxic T-Cells kill abnormal or infected cells using perforins
Perforins perforate the plasma membrane and cause cell death

7. III) The Specific Immune Response
Humoral Immune Response
B cells place markers on pathogens to alert complement proteins, macrophages, and natural killer cells to attack those cells
When B cells recognize antigens, they produce plasma cells
Plasma cells secrete large numbers of circulating antibodies to fight the antigens
Contain large amounts of endoplasmic reticulum and ribosomes for antibody production
Antibodies are proteins in a class known as immunoglobulins
B-Cells differentiate into Plasma Cells and Memory Cells in a process called clonal selection
Memory cells remain in blood for future infections

8. III) The Specific Immune Response
Recognition of Self
Major Histocompatibility Complexes (MHC)
Genes that produce glycoprotein cell surface receptors
MHC proteins serve as markers for the immune system that function in identification of cells as “self”
MHC proteins are used to determine tissue types for organ transplants
Identical twins have the same MHC proteins
Rarely unrelated individuals may have the same MHC proteins due to random chance
170 different markers may results in a random chance for the same combination of proteins

9. IV) Antibodies Proteins consisting of two polypetide chains
Light chain and heavy chain
Ends of the chains are the variable region
Specific chemical nature and structure
Binds to antigen
Antibody functions
“Label” antigens for attack by other immune cells
Cause agglutination of cells (clumping of cells)
Destroy cells and cause lysis
Inactivate toxic compounds

10. V) Primary and Secondary Responses
Primary Immune Response
Occurs the first time the body encounters a pathogen
Binding of an antigen stimulates B-cell division (clonal selection).
Recognition of the antigen is required before immunity is established
Primary response includes:
Fever
Symptoms of infection/illness
Slower response as immune system recognizes antigen
Secondary Response
Occurs with future exposure to the same antigen
Memory B-Cells recognize the antigen and immediately differentiate into plasma cells
Antibodies are secreted in large quantities
Antigen is quickly destroyed
No fever, no symptoms

11. VI) Acquiring Immunity
Active Immunity
Antigen enters the body
Infection by virus, bacteria
Vaccination
Weakened forms of the antigen injected to promote memory cell development
Results in permanent immunity to the antigen
Passive immunity
Antibodies from another source introduced into the body
Confers temporary immunity
Antibodies are NOT produced by the body
Need to reintroduce antibodies to maintain immunity
Tetanus shots
Immunity passed from mother to child through the placenta
Immunity passed through breast milk
Colostrum - clear fluid that contains mother’s antibodies

12. VII) Immune Disorders Autoimmunity
Immune cells attack healthy body cells
Results in damage and organ failure
Common autoimmune diseases
Juvenile Diabetes
Pancreatic islets cells destroyed – no insulin production
Multiple Sclerosis
Schwann cells destroyed causing a loss of myelin and loss of nerve function
Rheumatoid Arthritis
cartilage is destroyed causing pain and swelling in all joints
Lupus Erythematus
skin, connective tissue, muscles, kidneys, eyes are attacked

13. VII) Immune Disorders Acquired Immune Deficiency Syndrome (AIDS)
Caused by HIV (Human Immunodeficiency Virus)
HIV infects Helper T-cells and destroys them
Immune response decreases as helper-T-cell count decreases
The immune system becomes incapable of mounting a response to a foreign antigen
No direction and identification of antigens
Opportunistic infections damage body
Increased rate of cancer cell growth
Allergies
Hypersensitivity to non-pathogenic antigens
Massive histamine response
Can cause anaphylaxis
Rapid heart rate, difficulty breathing, abdominal pain, swelling of throat, face, eyes, hands, feet
Blood vessel dilation and very low blood pressure
May cause death