Download Chapter 19a

TORTORA • FUNKE
• CASE
Microbiology
AN INTRODUCTION
B.E Pruitt & Jane J. Stein
Chapter 19, part A
Disorders Associated with the
Immune System
Disorders Associated with the
Immune System
The Immune system does not always run perfectly
• It may over respond - hypersensitivities
– Hypersensitivities ~ allergy
• 4 types
– I, II and III - are humoral
– IV is cellular
• It may react to your own cells - Autoimmune
• Immune Deficiencies - unable to response to new
pathogens
Hypersensitivity Reactions
• Response to antigens (allergens) leading to damage
• First exposure to antigen called “allergen” sensitized, second - over
reaction
• Skin testing
• Desensitization can help improve reaction in about 70% of individuals.
– Produce IgG to antigen (allergen) and hide it from Mast cells and IgE’s
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Hypersensitivities
• Type I — Anaphylaxis. Mast cells degranulate when IgE
antibodies on surface bind to pathogens or allergens
(antigens that invoke too strong a reaction)
• Type II — Antibodies react with cell-surface antigens or
cells you own or that have been put in you
• Type III (Immune Complex) — IgM, IgG, complement
immune complexes deposit in tissues
• Type IV — Mediated by TD cells
Type I (Anaphylactic) Reactions
Type I
• anaphylaxis - against
protection
• May be localized or
systemic
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Figure 19.3
Type I (Anaphylactic) Reactions
Involves IgE antibodies and
Degranulation of Mast
Cells
– Histamine and mediators of
anaphylatics
• Localized: Hives or
asthma from contact or
inhaled antigens and
allergies - dust mite feces,
animal dander
– hay fever upper respiratory
– asthma lower respiratory
• Systemic: Shock from
ingested or injected
antigens like drugs, insect
venom,
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Figure 19.1a
Mast Cells
Figure 19.1
Type II (Cytotoxic) Reactions
Cytotoxic
• Involve IgG or IgM antibodies and
complement
• Cell bound Ag
• Host cells with foreign antigen or drug
acting as one
• Complement activation causes cell lysis,
inflammation or damage by
macrophages
• Transfusion reactions
• Rh incompatibility
Autoimmunity examples:
• Grave’s disease (thyroxin receptors)
• Myasthenia Gravis (ACh receptors)
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ABO Blood Group System
Table 19.2
Hemolytic Disease of the Newborn
Figure 19.4
Hemolytic Disease of the Newborn
• RhoGAM
Anti-Rh
• Gamma
globulin
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Drug-induced Thrombocytopenic Purpura
Disseminating
Intravascular
Coagulation
•DIC is a disorder
of diffuse
activation of the
clotting cascade
that results in
depletion of
clotting factors in
the blood.
Figure 19.5
Type III (Immune Complex) Reactions
• IgG, IgM and complement and antigens form complexes that
lodge in basement membranes.
• Small soluble complexes activate complement cascade
• Glomerulonephritis, Lupus, rheumatoid arthritis
Figure 19.6
–
–
–
–
–
Type IV
Cell mediated
1 - 2 day delay
T-cells attack tissue they shouldn’t
Rejection of transplanted tissues
Insulin - dependent diabetes
mellitus
– Skin test for Mycobacterium
tuberculosis and M. leprae
– Allergic dermatitis
• Poison oak and ivy
• Cosmetics, metals in jewelry
• detergents
Type IV (Cell-Mediated) Reactions
• Delayed-type
hypersensitivities due to
TD cells
• Cytokines attract
macrophages and initiate
tissue damage
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Figure 19.8
Autoimmune Diseases
• Clonal deletion during fetal development ensures selftolerance
• Autoimmunity is loss of self-tolerance
Reactions Related to the Human Leukocyte
Antigen (HLA) Complex
• Histocompatibility antigens: Self antigens on cell surfaces
• Major histocompatibility complex (MHC): Genes encoding
histocompatibility antigens
• Human leukocyte antigen (HLA) complex: The group of
MHC genes on leukocytes
Diseases Related to Specific HLAs
Table 19.3
Reactions to Transplantation
• Transplants may be attacked by T cells, macrophages, and
complement-fixing antibodies.
• Transplants to privileged sites do not cause an immune
response.
– Cornea, testes, brain, heart valves and fetal tissue
• Stem cells may allow therapeutic cloning to avoid rejection.
Organ rejection
Grafts
•
•
•
•
•
Autograft: Use of one's own tissue
Isograft: Use of identical twin's tissue
Allograft: Use of tissue from another person
Xenograft product: Use of non-human tissue
Graft-versus-host disease can result from transplanted
bone marrow that contains immunocompetent cells
Immunosuppression prevents an immune
response to transplanted tissues
• Cyclosporine
suppresses IL-2
• Mycophenolate mofetil
inhibits T cell and B
cell reproduction
• Sirolimus blocks IL-2
Immune Deficiencies
• Congenital: Due to defective or missing genes
– Selective IgA immunodeficiency
– Severe combined immunodeficiency
• Acquired: Develop during an individual's life, due to drugs,
cancers, infections
– Artificial: Immunosuppression drugs
– Natural: HIV infections
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The Immune System and Cancer
•
•
•
•
Cancer cells possess tumor-specific antigens
Immunological surveillance
Tc cells seek out and recognize cancer cells
Tc cells lyse cancer cells
Figure 19.11
Immunotherapy
• Treatment of cancer using
immunologic methods
• Tumor necrosis factor, IL-2, and
interferons may kill cancer cells
• Immunotoxins link poisons with an
monoclonal antibody directed at a
tumor antigen like ricin
– ribosome-inactivating proteins" (RIPs)
• Vaccines contain tumor-specific
antigens
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