Immune system

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Immune system

• Chapter 43

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• Pathogen
• Infectious agent
• Innate immunity
• Nonspecific
• Acquired immunity
• Specific
• Previous exposure

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Defense

• First line
• Skin
• Second line
• Cell counterattack
• Third line
• Immune response (antibodies)

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First-line

• Skin
• 1. Impenetrable barrier
• 2. Oil sweat glands
• Skin pH at 3-5
• 3. Sweat contains lysozyme
• Enzyme that digests bacterial walls
• 4. Prevents water loss

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Skin
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First line

• Lysozyme in saliva
• Acid in stomach
• Digestive enzymes in gut
• Mucous in airways
• Cilia in airways
• Acidic urine

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First line
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Trachea
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Second line

• Invaders
• Lymphatic system
• Defense cells
• Adenoids, tonsils
• Thymus, spleen
• Lymph nodes, lymph capillaries ducts

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Lymphatic system
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Second line

• WBC
• Antimicrobial proteins
• Inflammatory response

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Second line

• Leukocytes (WBC)
• Circulating in the body
• 1. Macrophages (monocytes)
• Kill invaders by ingesting them
• Phagocytosis
• Ingestion

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Fig. 43-3
Microbes
PHAGOCYTIC CELL
Vacuole
Lysosome containing enzymes
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Second line

• 2. Neutrophils
• Most abundant WBC
• Phagocytosis
• Release chemicals that kill bacteria
• Also kills other neutrophils

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Second line

• 3. Eosinophils
• WBC
• Low phagocytic activity
• Parasite defense

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Second line

• Antimicrobial proteins
• 1. Complement system
• Proteins found in plasma
• Attack bacterial or fungal cell walls
• Cause cells lysis
• Signals other defense responses

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Second line

• 2.Interferons
• Paracrine polypeptide
• Protect cells in area of virus
• Prevent viral replication
• Cancer defense

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Second line

• 3. Natural killer cells
• Kill cells that are infected by a virus
• Help fight cancer cells

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Second line

• Inflammatory response
• Local, non-specific
• Histamines prostaglandins
• Vasodilation
• Increased blood flow to area
• Edema or swelling
• WBC (phagocytic), pus formation
• Shock, systemic

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Second line
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Second line

• Inflammatory response
• Elevated temperature (fever)
• Interleukin-1
• Released by Macrophages
• Directs hypothalamus to increase temp
• Helps stimulate defense response

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Third line

• Specific response
• Lymphocytes (B-cell orT-cell)
• Antibodies

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Third line

• Antigen
• Molecule that causes a specific immune response
• Foreign to body
• Located on surface
• Epitope
• Antigen determinant

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Third line

• Self-versus-nonself recognition
• Genes code for specific proteins
• Major Histocompatibility Complex proteins
• MHC proteins
• Cell recognition
• Glycoproteins on surface of cells

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Third line

• B-cell lymphocytes
• Made develops in bone marrow
• Becomes a plasma cell
• Produce antibodies in response to specific
  antigens
• Immunoglobulins (Ig)
• Antibodies
• Humoral immunity

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Third line

• B-lymphocyte structure
• Antigen receptor
• Specific
• Plasma membrane

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Third line

• Light chains
• 2 short polypeptides
• Heavy chains
• 2 identical long polypeptides
• 4 chains held together by disulfide bond
• Forms Y-shaped molecules

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Fig. 43-9a
Antigen- binding site
Antigen- binding site


Disulfide bridge
V
V
V
V
Variable regions
C
C
Constant regions
C
C
Light chain
Transmembrane region

Plasma membrane
Heavy chains
Cytoplasm of B cell
B cell
(a) B cell receptor
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Fig. 43-10
Antigen- binding sites
Epitopes (antigenic determinants)
Antigen-binding sites


Antigen
Antibody A
Antibody C
V
V
V
V
C
C
C
C
Antibody B
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Antibodies

• Plasma cells release antigen receptor
• Specific for antigens
• Arms of the Y shaped molecule
• Have different aa sequences

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Antibodies

• IgM first response
• Aggregation of complement proteins
• IgG major form, second response
• Stimulates phagocytosis by macrophages
• IgD receptors for antigens on B cells
• IgA
• Present in breast milk, mucous, saliva
• Provide protection to newborns

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Antibodies

• IgE
• Release histamines
• Bind to mast cells
• Insert heavy chain into mast cells
• Initiate inflammatory response
• Presence of antigens
• Vasodilation

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Antibodies
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Third line

• T-cell lymphocytes
• Made in bone marrow
• Processed in thymus gland
• Regulate immune responses
• Attack cells with specific antigens
• Cell-mediated immunity

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Fig. 43-9b
Antigen- binding site

Variable regions
V
V
Constant regions
C
C
Transmembrane region

Plasma membrane
? chain
? chain
Disulfide bridge
T cell
Cytoplasm of T cell
(b) T cell receptor
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Third line

• T-cells
• 1. Helper T cells (CD4)
• Initiate response based on antigens
• 2. Memory T cells
• Remember previous antigens

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Third line

• 3. Cytotoxic T cell (CD8)
• Lyse cells infected by virus
• 4. Suppressor T cells
• Turn off immune response

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Third line response

• Antigen
• Macrophage process antigen
• Secrete cytokines (interleukins or interferons)
• Stimulates T helper cells

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Third line response

• Recognize antigens
• Antigen receptor on T-cells
• Bind to antigens
• Triggers T-cytotoxic cells, T-memory cells
• Cytotoxic cells destroy infected cells
• Stimulates B cells

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Third line response

• Antigen receptor on B-cell
• Binds foreign antigen
• Triggers formation of a clone of plasma cells
• Clones produce antibodies
• Antibodies bind invading antigen
• Prevent affects of antigen
• Destruction or blocks effect

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Immune response

• Macrophage
• ?
• Helper T-cell
• ? ?
• B-cell Cytotoxic T-cell
• ? ? ? ?
• Plasma Memory Memory Cytotoxic
• cells cells cells
  T-cells
• ?
• Antibodies

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T-cells

• Cytotoxic T-cells
• Attack transplants (skin grafts)
• Considered foreign tissue
• Destroy cancer cells
• Interferon (lymphomas, renal Ca, melanoma,
  Kaposis sarcoma and Breast Ca)
• Interleukin (tx cancer)

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B-cells

• Primary immune response
• First exposure
• Lasts about 2 weeks
• Memory cells are also produced during the first
  exposure
• Secondary immune response
• Activates memory cells
• Response faster lasts longer

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Immune System Summary

• First line
• Skin, cilia, enzymes, pH of skin
• Second line
• WBC (macrophages, neutrophils, natural killer
  cells, eosinophils)
• Antimicrobial proteins
• Inflammatory response

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Immune System Summary

• Third line
• Lymphocytes (B T)
• Antibodies (immunoglobulins)
• IgM, IgG, IgA, IgE, IgD

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Monoclonal antibodies

• Antibodies specific for one antigen
• Cell cultures produce large quantities
• Use in lab tests
• Pregnancy tests
• Antibody to HCG (human chorionic gonadotropin)

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Immunity

• Acquired immunity
• Active
• Disease
• Vaccine
• Transfer of lymphocytes from a donor (bone marrow
  transplant)
• Passive
• Maternal antibodies
• Immunoglobulins (gamma globulins)

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HIV

• Human immunodeficiency virus
• Attacks destroys CD4 T-cells
• T-cells secrete a suppressing factor
• Blocks other T-cells
• Infects macrophages brain cells

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HIV
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AIDS

• Acquired immunodeficiency syndrome
• Opportunistic infections
• Pneumocystis carinii
• Kaposis sarcoma
• Neurological damage
• Physiological wasting

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Autoimmune diseases

• Systemic Lupus
• Rheumatoid arthritis
• Hashimoto thyroiditis

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Allergy

• Allergens (antigens)
• Release IgE
• Binds mast cells basophils
• Stimulates release of chemicals
• Histamine
• Drop in BP

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Allergy

• Anaphylactic shock
• Widespread histamine response
• Death
• Bee stings or peanuts or penicillin
• Contact dermatitis
• Delayed response
• Poison ivy, poison oak

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Blood types (ABO)
Blood type Surface antigens Antibodies
A A anti B
B B anti A
AB AB none
O none anti A B
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ABO
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Rh factor