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The Immune System. (Chapter 43). Raj Patel AP Biology 4/27/12. What Is It?. The Immune System is designed to help protect the human body from outside threats These threats include viruses, bacteria, and other pathogens - PowerPoint PPT Presentation
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The Immune The Immune System System
The Immune The Immune System System (Chapter 43)
Raj PatelAP Biology4/27/12
The Immune System is designed to help protect the human body from outside threats
These threats include viruses, bacteria, and other pathogens
There are two types of immunity defense: Innate Immunity and Acquired Immunity.
What Is It?What Is It?What Is It?What Is It?
Present at start of birth and provides broad defense
Has both external and internal defenses:
Innate ImmunityInnate ImmunityInnate ImmunityInnate Immunity
1) Skin = barrier that is hard to penetrate 2) Mucous membranes = digestive and
respiratory tract linings that make mucus (traps microbes)
3) Secretions = saliva, tears, etc. Has lysozymes that digest bacterial cell walls.
External External Defenses Defenses External External
Defenses Defenses
(1) (2) (3)
1) Phagocytes = attach to bacteria’s surface polysaccharide receptors form lysosome vacuoles engulf bacteria
Internal Internal Defenses Defenses Internal Internal
Defenses Defenses
Types:-Neutrophils enter bacteria site and then engulf, but then self-destruct
-Macrophages reside in lymphatic tissue and capture bacteria via netlike extensions
-Eosinophils discharge destructive enzymes
-Dendritic cells can also engulf bacteria
2) Antimicrobial proteins = impede microbe reproduction through interferons
3) Natural Killer cells = kill virus-infected/cancer cells by releasing chemicals that cause apoptosis (programmed cell death)
4) Inflammatory response = histamine chemical increases blood flow to bacteria site and helps clot
Internal Internal Defenses Defenses Internal Internal
Defenses Defenses
Main proteins are cytokines, which help activate other cells in the immune system (reaction pathway)
Antigen = any molecule that elicits a response from cytokines
Epitope = portion of antigen that cytokines can bind onto in order to recognize molecule
Acquired Acquired ImmunityImmunityAcquired Acquired ImmunityImmunity
2 Types of lymphocytes: 1) B lymphocytes (B cells) – receptors for antigens are Y-
shaped and have 4 polypeptide chains (2 heavy and 2 light).
2) T lymphocytes (T cells) – receptors for antigens have 2 polypeptide chains, α chain and β chain, attached by disulfide bridge
MHC (major histocompatibility complex) attach to antigen and are recognized by T cells.
Class I MHC = found on all cells; bind peptides derived from foreign antigens that are synthesized in the cell
Class II MHC = bind peptides from foreign antigens that are fragmented, or broken, from phagocytosis/endocytosis
Acquired Acquired ImmunityImmunityAcquired Acquired ImmunityImmunity
Lymphocytes arise from stem cells in the bone marrow
B cells develop entirely in bone marrow T cells develop in thymus
Lymphocyte Lymphocyte DevelopmentDevelopmentLymphocyte Lymphocyte DevelopmentDevelopment
Nearly impossible for two B cells to have same exact receptors (same for T cells)
Each person has 1 million different B cells and 10 million different T cells
Differentiation is a result of random gene rearrangements in mRNA sequences
Lymphocyte Diversity Lymphocyte Diversity Lymphocyte Diversity Lymphocyte Diversity
When an antigen selects a B or T cell, the stimulated lymphocyte divides into 2 clone daughter cells
1st clone is made of many effector cells that combat the same antigen (short-lived)
2nd clone is made of memory cells that have receptors for specific antigens (long-lived)
Clonal Selection of Clonal Selection of LymphocytesLymphocytes
Clonal Selection of Clonal Selection of LymphocytesLymphocytes
Clonal Selection – antigen driven cloning of lymphocytes; consists of the steps:
Primary Immune Response – peaks after 10-17 days after initial exposure to antigen. Plasma cells (secrete antibodies) are made.
Secondary Immune Response – peaks after only 2-7 days after secondary exposure. This response is faster, stronger, and longer.
Clonal Selection of Clonal Selection of LymphocytesLymphocytes
Clonal Selection of Clonal Selection of LymphocytesLymphocytes
Acquired immunity is separated into 2 main branches: humoral immune response and cell-mediated response.
Humoral defends against pathogens toxins. Cell-mediated defends against infected cells, cancer cells, and tissues.
Humoral/Cell-Mediated Humoral/Cell-Mediated ImmunityImmunity
Humoral/Cell-Mediated Humoral/Cell-Mediated ImmunityImmunity
Helper T Cells – when it recognizes an antigen, it separates into clones and secrete cytokines that stimulate nearby lymphocytes.
Cytotoxic T Cells – uses a surface protein CD8 that keeps the binding between antigen and T cell strong. Used against cancer/infected cells.
T CellsT CellsT CellsT Cells
A Overview of the Immune System and Its Cells
LINK
B Cells differentiate into a clone plasma cell and a clone memory B cell once stimulated.
Once finished, the B cell sends the fragmented remains of the antigen to a helper T cell to finish off.
B CellsB CellsB CellsB Cells
There are 5 main types of antibody classes:
Antibody ClassesAntibody ClassesAntibody ClassesAntibody Classes
Active immunity – immunity response that is triggered by exposure to an infectious molecule.
Immunization (Vaccination) - develops prior to an active immunity response and depends on a cell’s memory of the antigen.
Passive immunity – immunity response that is triggered when antibodies from an immune person is transferred to someone who is not.
Active and Passive Active and Passive ImmunityImmunity
Active and Passive Active and Passive ImmunityImmunity
Type A blood cells have the A antigen on the surface Type B blood cells have the B antigen on the surface Type AB blood cells have both A and B antigens on the
surface Type O blood cells have neither on the surface
Blood Groups and Blood Groups and TransfusionsTransfusions
Blood Groups and Blood Groups and TransfusionsTransfusions
How Do They Work?How Do They Work?How Do They Work?How Do They Work?
Acceptable Transfusions:Acceptable Transfusions:Acceptable Transfusions:Acceptable Transfusions:
Sometimes, responses from the immune system can lead to diseases and conditions that are a result of the response.
Allergies are exaggerated (very sensitive) responses to specific antigens called allergens that trigger the response.
In this case, plasma cells secrete antibodies usually on pollen grains (hence, “spring allergies”). When the pollen grains enter the body again, they induce the cell to release histamine and other inflammatory molecules (called degranulation).
As part of the inflammatory response and increased blood vessel flow, symptoms like sneezing, runny nose, watery eyes, and itchy nose can result.
Immune Response Side-Immune Response Side-EffectsEffects
Immune Response Side-Immune Response Side-EffectsEffects
AllergiesAllergiesAllergiesAllergies
Autoimmune diseases – diseases that are triggered when immune system loses tolerance against itself.
Antibodies targeted against the body’s own natural molecules (histones, DNA breakdown) are released and various diseases can result.
Ex.) Lupus – disease characterized by skin rashes, fever, arthritis, and organ
dysfunction.
Autoimmune DiseasesAutoimmune DiseasesAutoimmune DiseasesAutoimmune Diseases
These deficiencies result from defects in the basic development of immune system cells. Both innate and acquired defenses can be seriously impaired.
Inborn (Primary) Inborn (Primary) Immunodeficiencies Immunodeficiencies
Inborn (Primary) Inborn (Primary) Immunodeficiencies Immunodeficiencies
Acquired (Secondary) Acquired (Secondary) Immunodeficiencies Immunodeficiencies Acquired (Secondary) Acquired (Secondary) Immunodeficiencies Immunodeficiencies These deficiencies can develop later in life and are
caused by some external agent as opposed to natural birth causes.
Serious developments can impair the immune system
Hodgkin’s Disease – damages the lymphatic system
AIDS (Acquired Immunodeficiency Syndrome) – this infamous condition makes infected people severely susceptible to immune system breakdowns even from the most basic coughs, fevers, colds, etc.