Chapter 4: Alterations in Immunity

Learning Objectives

• Describe cellular components: lymphocytes, macrophages, antigen-presenting cells, adaptive immune response.
• Differentiate between innate and adaptive immune responses.
• Define primary and secondary antibody responses in immunity development.
• Outline similarities and differences between T lymphocytes and active cell-mediated immunity.
• Discuss antibodies/immunoglobulins (IgA, IgD, IgE, IgG, IgM).
• Compare immune function associated with host defense failure, hypersensitivity, autoimmunity, alloimmunity.
• Describe interactions between cell-mediated and humoral immune response.
• Explore clinical models related to altered immunity.

Anatomy and Physiology of the Lymphatic System

• Lymphatic system is crucial for immune response.
• Central organs: bone marrow, thymus.
• Peripheral organs: spleen, lymph nodes, lymphoid tissue.
• Immune defense is the third line of defense after the inflammatory response.
• Involves recognition and neutralization of pathogens.

Immune Response Overview

• Innate Immunity: Nonspecific, no memory of previous pathogens.
• Adaptive Immunity: Specific, memory component, involves lymphocytes (T & B cells).

Types of Adaptive Immunity

• Active Immunity: Developed antibodies through disease or vaccination (e.g., flu vaccine).
• Passive Immunity: Transferred from host to recipient (e.g., mother to embryo via vaccination or breast milk).

Humoral Immunity

• Specific to development of antibodies by B lymphocytes.
• Immunoglobulins (antibodies) are secreted from B lymphocytes.

Primary vs Secondary Adaptive Immune Response

• Primary: First exposure, IgM is the initial antibody.
• Secondary: Reactivation, IgG mounts a more aggressive response.

Immunoglobulins

• IgM: Primary response, initial surveillance and response.
• IgG: Most abundant, secondary response, aggressive.
• IgA: Involved in passive immunity, transferred from mother to newborn.
• IgD: Stimulates B lymphocytes development.
• IgE: Associated with anaphylaxis and allergic reactions.

Cellular Components of Adaptive Immunity

• B Lymphocytes: Origin in bone marrow, part of humoral immunity.
• T Lymphocytes: Origin in thymus, part of cell-mediated immunity.
  • Cytotoxic T cells: Destroy antigen-carrying cells.
  • Helper T cells: Enhance humoral and cell-mediated response.
  • Suppressor T cells: Inhibit response post-infection.

Differentiation Cells

• CD8: Associated with cytotoxic T cells.
• CD4: Associated with helper T cells.
• MHC Cells: Present foreign body portions to immune system.

Alterations in Immune Function

• Hypersensitivity: Four types (Immediate, Mistaken identity, Non-soluble complexes, Delayed).
• Host Defense Failure: Antigenic variation, viral latency, immunodeficiency (primary and secondary).
• Alloimmunity: Response to foreign cells from same species (e.g., graft rejection).
• Autoimmunity: Body attacks itself, leading to systemic damage (e.g., lupus).

Alterations Goals

• Prevention with vaccines.
• Immunosuppression for autoimmune disorders using drugs (corticosteroids, cytotoxic drugs).
• Cancer therapy aims to destroy altered cells while sparing normal cells.

Clinical Models of Altered Immunity

• AIDS: Secondary immunodeficiency by HIV, systemic effects, diagnosed by antibodies and viral load.
• Anaphylaxis: Life-threatening allergic reaction, IgE-mediated, requires immediate treatment.
• Lupus: Chronic autoimmune response, systemic effects, diagnosed by lab tests.
• Rh Isoimmunization: Type 2 reaction between mother and fetus, potentially life-threatening for fetus.

Study and Review

• Complete guided learning questions, review textbook, disease cards, case studies, and class activities. Reach out for questions.