Antibody-Mediated Hypersensitivity (Type II) PDF
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Summary
This document provides an overview of antibody-mediated hypersensitivity, focusing on Type II hypersensitivity. It describes the mechanisms involved in the response, highlighting the role of IgG and IgM antibodies, complement activation, and antibody opsonization. It discusses the damages, effects, and different types of immune-mediated hemolysis, including alloimmune hemolysis, autoimmune hemolysis, and the involvement of B cells. Information is also given about antibody-mediated response against solid tissues and cell function. These responses are also described in the context of various diseases.
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Antibody-Mediated Hypersensitivity (Type-II) IgG and IgM bind to surface of cells: - Complement (C) activation - Antibody opsonization - Hormonal receptor binding Damages/effects: - Red cells - Solid Tissues - Functional effects (sometimes type V HPS) Immune-mediated Hemo...
Antibody-Mediated Hypersensitivity (Type-II) IgG and IgM bind to surface of cells: - Complement (C) activation - Antibody opsonization - Hormonal receptor binding Damages/effects: - Red cells - Solid Tissues - Functional effects (sometimes type V HPS) Immune-mediated Hemolysis Red Cells Antigens - ABO and Rh antigens: # ABO: Oligosaccharides IgM natural Ab # Rh: Protein IgG # I-system: Self-antigen; important in auto- immunity (e.g. Auto-Immune Hemolytic Anemia “AIHA”). Anti-Red Cell Antibodies 1. IgM # Effective C – activator (MAC) damage cells (e.g. RBC) 2. IgG # Not very effective C- activator # Opsonization Macrophages (FcR)- phagocytosed fragments of cells (RBC) Types of Immune-Mediated Hemolysis Alloimmune Hemolysis - Hemolytic disease of New born # Gradual destruction of fetal IgG-coated RBC by macrophages in spleen/liver - Incompatible ABO- blood transfusion # Very fast (in seconds) by IgM natural Ab IgM (pentamer) very good C-activator Aggregate (agglutinate) RBC (activate complement) Autoimmune Hemolysis - AIHA triggered by infections or drugs; or part of autoimmune disease (AID) as SLE # B-CLL Autoantibodies (AIA) # AIHA: - IgG-autoantibodies (Warm Ab) - IgM- autoantibodies (Cold Ab) which are active below 37 Celsius Type II Autoimmune Hypersensitivity Against Solid Tissues 1. Goodpasture’s syndrome (GPS) # IgG anti-basement membrane (BM) of lungs and glomeruli Activate C 2. Pemphigus (blistering skin condition) # IgG binds to intercellular cement protein (desmoglein) 3. Myasthenia gravis # IgG binds to acetylcholine receptor in skeletal muscles Weakness Type II HPS and Antibodies that affect cell function Graves’ Disease (Type V HPS “Stimulatory” - Most common cause of hyperthyroidism - Often in young women/with family history # Linked to HLA-DR3 - Auto-Antibodies (IgG) bind to TSH receptor (mimics TSH hormone stimulation) - Exophthalmos (protruding eyes): # T cells infiltrate orbit; autoimmune reaction
