Pharmacy 310: Immune Disorders Overview

Allergy & Hypersensitivity

• Allergy results from the immune system's overreaction to non-harmful environmental antigens, affecting 10-40% of individuals in developed countries.
• Anaphylaxis is a severe, life-threatening allergic reaction characterized by rapid onset.

Types of Hypersensitivity Reactions

• Four types are classified based on their effector mechanisms:
  • Types I, II, and III are mediated by antibodies.
  • Type IV is mediated by cytotoxic T-cell products.

Type I Hypersensitivity (Anaphylactic)

• Usually triggered by inhaled antigens (e.g., pollen, dust mites).
• Antigens bind to specific IgE antibodies on granulocytes, leading to degranulation and release of inflammatory mediators.
• Mast cells release immediate (pre-packaged) mediators and later synthesize additional mediators post-activation.

Mast Cell Responses

• Mast cells synthesize Prostaglandins and Leukotrienes from Arachidonic Acid, a breakdown product of cell membrane fatty acids.

Eosinophil Response

• Eosinophils are primarily found in connective tissues and play a crucial role in combating parasites, but can also damage host tissues.
• The expression of Fcε (epsilon) and Complement receptors on eosinophils is regulated by inflammation.

Routes of Allergen Exposure

• The exposure route determines the type of allergic response; for instance, inhalation can lead to allergic asthma, whereas ingestion may cause food allergies.

Immediate vs. Late-Phase Allergic Reactions

• IgE-mediated reactions have an immediate response followed by a late-phase reaction, seen in conditions like allergic asthma and rhinitis.

Treatment Strategies for Allergic Reactions

• Prevention involves avoiding allergens.
• Pharmacological treatments include antihistamine blockers, corticosteroids, Cromolyn sodium, and epinephrine for anaphylaxis.
• Immunological approaches focus on desensitization and shifting the immune response from IgE to IgG4.

Type II Hypersensitivity (Cytotoxic)

• Caused by small molecules attaching to human cell surfaces, leading to cell destruction recognized by the immune system.
• Antibiotics like penicillin can trigger Type II hypersensitivity.

Type III Hypersensitivity (Immune Complex)

• Arises from the deposition of immune complexes on blood vessel walls, leading to tissue damage through inflammatory responses.
• Serological reactions can follow therapeutic administration of foreign proteins, causing symptoms like fever and rash.

Type IV Hypersensitivity (Delayed-Type)

• Mediated by T-cell responses, primarily CD4 TH1 cells.
• Associated with chronic conditions, including organ transplant rejection and autoimmune diseases.

Autoimmune Diseases

• Characterized by misdirected immune responses against healthy cells, classified into Type II, III, and IV types based on underlying mechanisms.
• Autoimmune responses can worsen over time and may lead to severe health consequences.

Association with Infections

• Infections can trigger autoimmune responses, evidenced in conditions like rheumatic fever following Streptococcus infections and Lyme Disease leading to autoimmune arthritis.

Genetic Factors in Autoimmunity

• Susceptibility to autoimmune diseases is often familial and linked to specific HLA genes, contributing to disease predisposition across ethnic groups.

Summary of Autoimmune Responses

• Type II autoimmune diseases involve antibodies against cell surface antigens.
• Type III diseases result from immune complexes, while Type IV diseases are mediated by T-cells.

This quiz covers key concepts in immune disorders, specifically focusing on allergy and hypersensitivity reactions as well as autoimmune diseases. Learn about the differences, mechanisms, and implications of these conditions within the context of pharmacy and pharmaceutical sciences.