Alport syndrome is characterized by antibodies act against?
**Core Concept**
Alport syndrome is a genetic disorder characterized by glomerulonephritis, end-stage kidney disease, and hearing loss, primarily due to mutations in the COL4A3, COL4A4, and COL4A5 genes encoding type IV collagen. The disease process involves the immune system's response to abnormal collagen in the glomerular basement membrane.
**Why the Correct Answer is Right**
The correct answer involves the immune system's role in Alport syndrome. Patients with Alport syndrome develop antibodies against type IV collagen, specifically against the alpha 3, alpha 4, and alpha 5 chains. These antibodies are primarily directed against the non-collagenous domain 1 (NC1) region of the type IV collagen molecules. The immune response is thought to be mediated by T cells and B cells, leading to the production of autoantibodies against the abnormal collagen.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the antibodies in Alport syndrome are not directed against the basement membrane's laminin or fibronectin components.
* **Option B:** This option is incorrect because the disease process involves autoantibodies against type IV collagen, not against the collagen type I or III.
* **Option C:** This option is incorrect because the immune response in Alport syndrome is not primarily mediated by complement system activation.
**Clinical Pearl / High-Yield Fact**
Alport syndrome is an X-linked dominant disorder, with the majority of cases resulting from mutations in the COL4A5 gene. Males are more frequently affected than females, who are often carriers of the disease.
**Correct Answer:** C. type IV collagen