Immune System: Ch 35
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Immune System: Ch 35
• Two major categories: innate & acquired immunity • Innate:
• present before any exposure to pathogens • effective from birth• involves nonspecific responses to pathogens• consists of external barriers + internal cellular and
chemical defenses• Key internal defenses are macrophages and other
phagocytic cells
Immunity intro
• Acquired (aka adaptive) :• develops after exposure to antigens
• antigen = • agents such as microbes, toxins, or other foreign
substances• It involves a specific response to pathogens
• Recognition is by white blood cells called lymphocytes• Some lymphocytes make antibodies; • others destroy infected cells, cancer cells, or foreign
tissue
Immunity intro
© 2014 Pearson Education, Inc.
Figure 35.2
INNATE IMMUNITY(all animals)• Recognition of traits shared by broad ranges of pathogens, using a small set of receptors• Rapid response
Barrier defenses:SkinMucous membranes SecretionsInternal defenses:Phagocytic cells Natural killer cells Antimicrobial proteins Inflammatory response
Humoral response:Antibodies defend against infection in body fluids.
Cytotoxic cells defendagainst infection in body cells.
Cell-mediated response:
ADAPTIVE IMMUNITY(vertebrates only)• Recognition of traits specific to particular pathogens, using a vast array of receptors• Slower response
Pathogens (such as bacteria,fungi, and viruses)
Immunity intro
Internal Cellular and Chemical Defenses• Internal non-specific cellular defenses depend mainly on
phagocytosis• WBCs called phagocytes. Function?• ingest microorganisms • initiate inflammation
• Phagocytes attach to prey. How? Then what?• via surface receptors • and engulf them, (then what? Think back to cell unit...)• forming a vacuole that fuses with a lysosome
• Macrophages (type of phagocyte) - where are they in body?• (migrate throughout the body) mostly in organs of
lymphatic system• Lymphatic Sys?• The lymphatic system helps defend vs pathogens
LE 43-4
PseudopodiaMicrobes
MACROPHAGE
Lysosome containing enzymes
Vacuole
Lymphatic System
Adenoid
Tonsil
Lymph nodes
Peyer’s patches (small intestine)
Spleen
Appendix
Lymphatic vessels Lymph
nodeMasses of lymphocytes and macrophages
Lymphatic vessel
Blood capillary
Tissue cells
Lymphatic capillary
Interstitial fluid
Acquired immunity: lymphocytes provide specific defense• A lymphocyte recognizes and binds to a small portion of the
antigen called:• epitope
Antigen- binding sites
Epitopes (antigenic determinants)Antibody A
Antibody BAntibody C
Antigen
Antigen Recognition by Lymphocytes• Two main types of lymphocytes:• B lymphocytes (B cells) • T lymphocytes (T cells)
• each B cell or T cell has about 100,000 identical antigen receptors• recognize the same epitope• receptors are:
• antibodies
B Cell Receptors for Antigens
• B cell receptors bind to specific, intact antigens• Some B cells secrete antibodies (aka immunoglobulins/Ig)
Lymphocyte Development
Lymphoidstem cell
Bone marrow
Thymus
T cell
Blood, lymph, and lymphoid tissues(lymph nodes, spleen, and others)
B cell
• Where are lymphocytes made?
• Start out alike but later develop into B cells or T cells• What determines their
fate?
Testing and Removal of Self-Reactive Lymphocytes• How do animals avoid attacking their own cells?• B and T-cell antigen receptors are tested for self-reactivity.
Where?• Lymphocytes with receptors for antigens that are already in
the body are destroyed by apoptosis or rendered nonfunctional
Clonal Selection of Lymphocytes: Primary immune response
Antibodies to A Antibodies
to B
• Clonal selection =• in 1˚ immune response:
• activated lymphocyte proliferates and differentiates• Clonal selection of B cells makes 2 types of memory cells:
• short-lived activated effector cells (plasma cells)• long-lived memory cells (long term immunity)
LE 43-12
B cells that differ in antigen specificity
Antigen molecules
Antigen receptor
Antibody molecules
Clone of memory cells Clone of plasma cells
• Memory cells facilitate a faster, more efficient response• How vaccination helps protect:• antigens in vaccine cause production of memory cells• sometimes multiple vaccinations needed• sometimes booster shots needed to help memory cells
persist
Secondary Immune Response
Blood Clotting
•cuts in skin sever blood vessels •blood oozing from cut turns into semi solid gel, sealing wound
•damaged tissue releases clotting factors (from platelets) that turn prothrombin into thrombin.
•thrombin turns (soluble) fibrinogen into (insoluble) fibrin
•fibrin acts like a mesh net, holding in cells
Coronary thrombosis
•clots in coronary arteries can lead to fibrillation and then death
•atherosclerosis causes occlusion in coronary arteries
•This can induce clotting in the coronary arteries
•Risk factors: •smoking •high blood cholesterol •high blood pressure •diabetes •obesity •lack of exercise
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Active and Passive Immunization
• Active immunization – develops in response to an infection – also develop following vaccination
• Vaccination (immunization) – nonpathogenic form of a microbe (or part
of a microbe) induces immunological memory
– polio, smallpox, diptheria, tetanus, whooping cough...
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Passive immunity provides immediate, short-term protection – It is conferred when IgG crosses the placenta
from mother to fetus – or when IgA passes from mother to infant in
breast milk – also by injecting antibodies into a non-immune
person
Active and Passive Immunization
Humoral and cell-mediated immunity
• Humoral immune response• involves activation and clonal selection of B cells• results in production of secreted antibodies
• Cell-mediated immune response • involves activation and clonal selection of cytotoxic T
cells
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The immune system’s ability to distinguish self from nonself limits tissue transplantation
• The immune system attacks cells from other individuals – Transplanted tissues are “other”
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Allergies
▪ Allergies are exaggerated (hypersensitive) responses to antigens called allergens
▪ ex: plasma cells secrete antibodies specific for antigens on the surface of pollen grains ▪ causes release of histamine and other
inflammatory chemicals ▪ Antihistamines block receptors for histamine
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Figure 35.17
IgE
Allergen
GranuleMast cell
1
2
Histamine
3
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▪ An acute allergic response can lead to anaphylactic shock, a life-threatening reaction
▪ (ex: bee venom, penicillin, peanuts, and shellfish) ▪ epinephrine counteracts the allergic response
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Acquired Immunodeficiency Syndrome (AIDS)
• The loss of helper T cells results from infection by the human immunodeficiency virus (HIV)
• People with AIDS are highly susceptible to opportunistic infections and cancers that take advantage of an immune system in collapse
AUTOIMMUNE DISEASES
• ex: Rheumatoid arthritis
• Other examples:• Systemic lupus erythematosus
• systemic attack on tissues• individual problems treatable, but no cure• more women than men
• Multiple sclerosis• myelin sheath destroyed• no cure
• Insulin-dependent diabetes• beta cells in Islets of Langerhans of pancreas
AUTOIMMUNE DISEASES
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