Type II hypersensitivity

Hypersensitivity

Also known as antibody-mediated disorders.

 

Examples

• Anti-glomerular basement membrane disease (Goodpasture's syndrome)
• Autoimmune haemolytic anaemia 
• Fetal erythroblastosis
• Graves disease
• Immune thrombocytopenia  
• Myasthenia gravis
• Pemphigus vulgaris
• Pernicious anaemia
• Rheumatic fever
• Vasculitis caused by ANCA

Mechanism

• Cell surfaces features antigen. This may be self-antigen (intrinsic) or foreign antigen adsorbed onto the surface (extrinsic). 
• Antigen presenting cells (APCs) bind the antigen and recruit B cells.
• B cells replicate (clonal expansion) and differentiate to plasma cells. These produce antibody (immunoglobulin) specific to that antigen.
• IgG and IgM antibodies (immunoglobulins) binds to antigen.
• Antibody complexes activate the classical pathway of complement activation. Mediators of acute inflammation (e.g. C3a, C3b, C9) are generated at the site. Membrane attack complexes cause cell lysis and death.
• Natural killer cells (NK) and macrophages recognise antibody tagged cells and induce cell lysis. This is called antibody-dependent cell-mediated cytotoxicity (ADCC).