The Immune System
Ch. 24
Objectives: Define and Comprehend
Nonspecific vs. specific immunity responses Different types of nonspecific responses Humoral vs. cell-mediated immunity
Nonspecific vs. specific defenses
Nonspecific defenses do not distinguish
one infectious microbe from another Specific defenses recognize and defend against invading microbes and cancer cells
1 minute brain storm
What is an immune system? What are the components of an immune system?
Nonspecific defenses
Skin is a barrier that most bacteria and viruses can’t penetrate
Acids secreted by skin prohibit growth of many microbes Sweat, saliva, and tears contain enzymes that attack bacterial cell walls
Mucus produced in digestive and respiratory systems also protects against microbes
Nonspecific defenses
Microbes that penetrate skin, digestive, or respiratory systems face neutrophils and monocytes
macrophages that “eat” bacteria and viruses
Interferons and complement proteins attack microbes either directly or indirectly by impeding their reproduction
Nonspecific defenses
Interferons are produced by infected cells
Diffuse to healthy cells where they cause the cell to inhibit viral production
Complement proteins are activated by microbes or immune system
Coat infected cells –easier to eat Can amplify inflammatory response
Nonspecific defenses: inflammatory response
Nonspecific defenses: inflammatory response
Redness, heat, and swelling caused by
Increase in blood flow, fluid, and cells
Inflammatory response disinfects and cleans injured tissues
Pus = dead white cells and fluid Toxins or microorganisms released in bloodstream
Systemic response is widespread
Circulates through body
Nonspecific defenses: inflammatory response
Systemic response cont’d.
Inflammatory weapons: increase white blood cells, fever
Low-grade fever can stimulate phagocytosis and inhibit growth of many microorganisms
Lymphatic system
Lymphatic system
Involved in both specific and nonspecific responses Lymphatic system defenses occur in lymph nodes and lymphatic system organs
Packed with lymphocytes and macrophages Lymph carries microbes from infection sites and some cancer cells In the lymphatic organs, macrophages may “eat” the invaders (nonspecific) Lymphocytes can be involved in specific immune response
Lymphatic system
Why do your lymph nodes swell when you are fighting certain kinds of infections?
Production of lymphocytes in nodes
IN PAIRS in your notebook
Describe the types of nonspecific responses your body has at its disposal if it were to be:
Invaded by a microbe Cut
Specific immunity
Often more effective than nonspecific response
It also amplifies nonspecific response
Specific response begins due to presence of an antigen
Can either increase number of cells that attack invader directly OR Produce antibodies
Immune system “remembers” antigens it has previously encountered
Responds immediately and vigorously Is adaptive
Specific Immunity
Vaccines:
D:\Vaccines\Vaccines.mpg
Objectives: Define & Comprehend
Role of clonal selection in immunity response Primary vs. secondary response Antibodies T cells Autoimmune vs. immunodeficiency diseases Allergies HIV/AIDS
Lymphocytes
Specific Immunity: Lymphocytes
Humoral system defends against bacteria and viruses present in body fluids
Fluids: blood, lymph, and interstitial fluid Antibodies, secreted by B cells and dissolved in the blood, are carried in lymph and blood to sites of infections T-cells circulate in blood and lymph Attack body cells that have been infected
Cell-mediated immunity
Specific Immunity: Lymphocytes
For BOTH humoral and cell-mediated immunity
B & T cells have antigen receptors (antibodies) that protrude from cell surface
specific for one type of antigen**
Each person has between 100 million to 100 billion different kinds of B & T cells!
Antigens
Most antigens are molecules that are present on viral surfaces or foreign cells B cells respond to free antigens in body fluid Different antibodies can bind to the same antigen
Specific immunity: clonal selection
Primary vs. Secondary immune response
Question
Why are “childhood” diseases referred to as such?
First exposure occurs during childhood, which then confers immunity during remaining years of the individual’s life
How do antibodies block invaders?
Antibodies bond to antigen molecules, which marks them and results in either:
An increase in the possibility of phagocytosis Activation of complement proteins that can cause the invader’s cell to rupture***
D:\ImageLibrary16-26\24-TheImmuneSystem\24-11AntibodiesAnim.mov
Role of T cells in Immunity
T cells battle pathogens that have already
entered body cells
Respond to antigens that have bonded to body cell surfaces Mount cell-mediated defense and aid humoral immunity
T cells
Cytotoxic T cells
Only T cells that kill other cells
Synthesize a protein that ruptures infected cell
Helper T cells
Secrete stimulatory proteins that help
Promote production of more helper T cells and memory cells Activate cytotoxic T cells Stimulate B cells to produce antibodies
Question
Why is it important that our immune system can distinguish self from nonself?
Cell identification tags enable immune system to determine the difference
Autoimmune Diseases
MS: T cells attack myelin –a protein that insulates the axons of neurons (a brain thing)
Most common chronic neurological disease in developed countries
Immunodeficiency diseases
SCID (Severe Combined Immunodeficiency): T and/or B cells are absent or inactive “bubble” people
Allergies
Stage 1
Stage 2
HIV/AIDS
HIV destroys the immune system by infecting helper T cells Eventually develop AIDS
Body cannot carry out cell-mediated or humoral response
Die from opportunistic infections
36.1 million people have HIV/AIDS 5.3 million new cases each year
Class Problem
Describe what happens when you get the flu
The first time The second time Include everything