Which condition is commonly associated with Type III hypersensitivity?

Which condition is commonly associated with Type III hypersensitivity?

• A. Asthma
• B. Type I diabetes
• C. Rheumatoid arthritis
• D. Multiple sclerosis

Answer: (C)

Type III hypersensitivity is immune complex–mediated tissue injury. When antibody–antigen complexes form and deposit in tissues, they activate complement and recruit inflammatory cells, causing that tissue damage. Rheumatoid arthritis is commonly linked to this mechanism because autoantibodies (rheumatoid factors) form immune complexes with IgG that deposit in the joint synovium, triggering complement activation and inflammatory damage that leads to the characteristic synovitis of RA. In contrast, asthma is driven mainly by IgE-mediated Type I hypersensitivity; Type I diabetes is primarily T-cell–mediated autoimmune destruction of pancreatic beta cells; multiple sclerosis is driven by T-cell–mediated demyelination (a Type IV hypersensitivity).

Type III hypersensitivity is immune complex–mediated tissue injury. When antibody–antigen complexes form and deposit in tissues, they activate complement and recruit inflammatory cells, causing that tissue damage. Rheumatoid arthritis is commonly linked to this mechanism because autoantibodies (rheumatoid factors) form immune complexes with IgG that deposit in the joint synovium, triggering complement activation and inflammatory damage that leads to the characteristic synovitis of RA. In contrast, asthma is driven mainly by IgE-mediated Type I hypersensitivity; Type I diabetes is primarily T-cell–mediated autoimmune destruction of pancreatic beta cells; multiple sclerosis is driven by T-cell–mediated demyelination (a Type IV hypersensitivity).