Immunopathology

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Immunopathology

• Normal hematopoiesis
• Immunity vs Inflammation
• Examples of hypersensitivity types I - IV
• Autoimmune diseases
• Graves disease
• Systemic lupus erythematosis
• Scleroderma
• Immunodeficiency (congenital acquired)

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Bone marrow stem cells give rise to various blood
cells through complex differentiation pathways.
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Normal Bone Marrow
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Bone Marrow Smear
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Clonal Proliferation of Erythroid Stem Cells In
Vitro
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What is Immunity? How is it distinguished from
inflammation?

• Antigenic Specificity
• Memory
• Mediated by B and T Lymphocytes

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Hypersensitivity Reactions

• Immediate (Type I)
• Cytotoxic (Type II)
• Immune complex (Type III)
• Delayed (Type IV)

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Type I Hypersensitivity

• Mast cells with cell surface IgE receptors
  degranulate and release vasoactive amines (eg
  histamine)

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Two Mechanisms Mediate Mast Cell Degranulation
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Type II Hypersensitivity

• Antibody-Mediated Cytotoxicity

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Role of Antibody and Complement in Opsonization
and Phagocytosis of a Foreign Object
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Patient with Graves Disease

• Hyperthyoidism
• Exophthalmia
• Patient has auto-antibodies to the TSH receptor
• This qualifies as a type 2 reaction

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Type III Hypersensitivity

• Immune Complex-Mediated Tissue Injury

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Immune Complex-Mediated Vascular Inflammation
(Vasculitis)
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Systemic Lupus Erythematosus

• Example of type 3 hypersensitivity reaction
  affecting skin and internal organs
• Systemic disease

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Clinical Features of Systemic Lupus Erythematosus
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Immune complexes identified by direct
immunofluorescence in a kidney biopsy from a
patient with lupus nephritis.
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Scleroderma
Scleroderma (Collagen Vascular Disease)
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Type IV Hypersensitivity

• Cell-Mediated (Delayed) Hypersensitivity Reaction

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T lymphocyte-mediated target cell killing.
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Immunodeficiency Diseases

• Congenital
• (eg selective IgA deficiency)
• Acquired
• (eg Human Immunodeficiency Virus)

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HIV Infection
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Clinical Features of Acquired Immunodeficiency
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Path Key Words

• Acquired immunodeficiency syndrome (AIDS)
• Adenosine deaminase deficiency
• Common variable deficiency
• Congenital X-linked hypogammaglobunemia
• Dermatomyositis

• DiGeorge syndrome
• Myasthenia gravis
• Raynaud phenomenon
• Scleroderma
• Selective IgA deficiency
• Sjogren syndrome
• Systemic lupus erythematosus