Which is not involved in Ankylosing spondylitis –
**Core Concept**
Ankylosing spondylitis (AS) is a type of inflammatory arthritis primarily affecting the spine and sacroiliac joints. It is characterized by chronic inflammation, leading to eventual fusion of the vertebrae and potential loss of spinal mobility. The pathogenesis of AS involves a complex interplay of genetic, environmental, and immune system factors.
**Why the Correct Answer is Right**
The correct answer is not specified, but I will provide explanations for each option. The key to answering this question is understanding the pathophysiology of ankylosing spondylitis. The condition is closely associated with the HLA-B27 gene, and the immune system plays a crucial role in its development. The primary inflammatory cells involved in AS are T lymphocytes, macrophages, and neutrophils, which infiltrate the affected joints and contribute to the chronic inflammation.
**Why Each Wrong Option is Incorrect**
* **Option A:** HLA-B27 is strongly associated with ankylosing spondylitis, and individuals with this genetic marker are at increased risk of developing the condition. Therefore, HLA-B27 is indeed involved in AS.
* **Option B:** T lymphocytes, macrophages, and neutrophils are the primary inflammatory cells involved in the pathogenesis of ankylosing spondylitis. Therefore, these cells are also involved in AS.
* **Option C:** The correct answer is not specified, but I will provide an explanation for a hypothetical option C. If option C were a correct answer, it would not be involved in ankylosing spondylitis. However, without knowing the specific option C, I will assume it is a distractor and provide an explanation for a common distractor. For example, if option C were "osteoblasts," it would be incorrect because while osteoblasts are involved in bone formation, they are not directly involved in the inflammatory process of ankylosing spondylitis.
**Clinical Pearl / High-Yield Fact**
A key clinical feature of ankylosing spondylitis is the presence of inflammatory back pain, often accompanied by stiffness and limited mobility. The condition is also associated with an increased risk of cardiovascular disease and gastrointestinal complications, such as inflammatory bowel disease.
**Correct Answer: D.**