Summary table of types of hypersensitivity reactions. Type 1 - Mediators: lgE - Antigen Form: Soluble antigen - Mechanism of Action: Allergen-specific lgE causes mast-cell degranulation releasing histamine and other inflammatory mediators - Time Course: Immediate-phase: minutes, Late-phase: 8-12 hours - Examples: Anaphylaxis, Hay fever, Food allergies, Drug allergies, Eczema, Asthma Type 2 - Mediators: IgG/ IgM - Antigen Form: Cell-bound antigen - Mechanism of Action: IgG/lgM antibodies bind to cell antigens, leading to complement activation and destruction of the cell - Time Course: Hours to days - Examples: Acute transfusion reaction, Haemolytic disease of the newborn Type 3 - Mediators: Antigen-antibody complex - Antigen Form: Soluble antigen - Mechanism of Action: Antigen-antibody complexes are deposited in tissues where they activate complement chain causing local inflammation and recruitment of leucocytes - Time Course: Hours to days - Examples: Rheumatoid arthritis, Post-streptococcal glomerulonephritis, Systemic lupus erythematosus Type 4 - Mediators: T cells - Antigen Form: Soluble/cell bound antigen - Mechanism of Action: Antigen-presenting cells activate Th1/cytotoxic T cells. T-cells recruit macrophages and release inflammatory cytokines - Time Course: Days (delayed) - Examples: Contact dermatitis, Tuberculin test, Graft rejection #hypersensitivity #reactions #types #allergy #table #classification #comparison
