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The Immune System
Transcript of The Immune System
Involves nonspecific responses to pathogens Checkpoint 1 How exactly does adaptive immunity work? Immune An animal must defend itself from the many dangerous pathogens it may encounter in the environment = Physical barriers Self-Tolerance Chapter 43 The Immune System Innate Immunity Skin Must distinguish self from nonself.
If a cell has receptors that react against its own epitopes, it will either self-destruct or be rendered nonfuctioning. A summary of the two defenses Two major kinds of defense have evolved that counter these threats: Innate immunity
Acquired immunity Develops only after exposure to inducing agents such as microbes, toxins, or other foreign substances
Involves a very specific response to pathogens Acquired Immunity Also called adaptive immunity [White Blood Cells] Phagocytes Mucous Membranes Secretions Produce mucous that traps particles provide hostile environment to microbes External Defenses Internal Defenses Ingest invading microorganisms
Initiate the inflammatory response
ex. neutrophil Introduction Video Pseudopodia
into cell. Vacuole
microbes forms. Vacuole
fuse. Toxic compounds and lysosomal enzymes destroy microbes. Microbial debris is released by exocytosis. Macrophages = "Big Eaters" Specific type of phagocyte found roaming around the body and throughout lymphatic system. Lymphatic System provides defense for the body Lymphatic capillaries filled with macrophages, dendrite cells, and lymphatic cells Inflammatory
Response Proteins trigger inflammation while interferons activate macrophages
Histamine and other chemicals are released from injured cells. Natural
Killer Cells Patrol the body and attack virus-infected body cells and cancer cells
Trigger apoptosis in the cells they attack NOTE:
Invertebrates perform many of the same innate response processes. = any foreign object that enters the body Antigen Lymphocytes recognize specific antigens and bonds to them at the epitope, or antigenic determinant. Types of Lymphocytes B Cells T Cells circulate through the blood
contain receptors on membranes Mature in bone marrow
Bind to specific, intact antigens Mature in thymus
Bind to small fragments of antigens that reside on MHC molecules of host cells MHC Molecules (major histocompatibility complex) Present on the plasma membranes of infected cells.
All cells contain MHC molecules. When a cell gets infected, the MHC molecule captures antigen fragments and brings it to the surface of a cell to be picked up by T cells. Before we dive into the processes of B and T cells, let's review... Proliferation There's very few lymphocytes that have the receptors for specific antigens.
When this cell is found through the process of clonal selection, it proliferates (multiplies) to produce
effector cells (short-lived)
memory cells (long-lived) Primary Immune Response Secondary Immune Response First introduction to an antigen - causing clonal selection.
[Antibodies are sent to attack the antigen] Memory cells facilitate a faster, more efficient response to the recognizable antigen. Two types of responses Humoral immune response
occurs in the blood and lymph, where antibodies eliminate pathogens. Cell-mediated immune response
occurs in cells, when T cells destroy host cells. 1. 2. Helper T Cells Cytotoxic T Cells Trigger both types of responses.
Antigen must be
1. able to attach to the T cell and
2. be presented on the surface of an
antigen-presenting cell - which can be dendrite cells, B cells, or macrophages.
Class II MHC
Activate cytotoxic T cells *Note: Host cells and antigen-presenting cells both display antigens on their surface, but the difference is in the MHC molecules they use to do so. Cell mediated response only
Use toxic genes to kill infected cells
Targeted host cell is completely destroyed once antigens are presented
Class I MHC B Cells Activation:
T cells activate B cells when it recognizes the antigen the T cell recently attacked
The B cell then proliferates into
1. memory B cells and
2. plasma cells that secrete antibodies Antibodies Ambush antigens, causing them to self-destruct, inactivate, or neutralize. [Various methods] Checkpoint 2 A summary of Acquired Immune Responses Disruptions in the Immune System Immunization Active Passive Natural immune response to an infection.
can also be in response to a vaccination Provides immediate, short-term protection,
when a mother passes through the placenta or her milk to an infant.
can also be given artificially to nonimmune individuals Adaptive Immunity can be blocked or misregulated EFFECTED IMMUNE RESPONSES ADAPTATIONS OF PATHOGENS CANCER 1. Allergies
= exaggerated response to a certain allergen.
2. Autoimmune disease
= immune system attacks itself
3. Effects of stress/exertion
= decreases the strength of the immune system.
4. Immunodeficiency disease
= the response to antigens is defective/absent
[AIDS] Antigenic Variation
= the pathogen changes appearance
= virus goes inactive after effecting the host
= infects helper T cells while escaping and immunicresponse *The frequency of cancer increases when adaptive immunity is inactive THE END But if everything doesn't work the right way...