Note a delayed type of hypersensitive reactions -a) Arthus reactionb) Bronchial asthmac) Hemolytic anemiad) Multiple sclerosis
**Core Concept**
The question requires the identification of a delayed type of hypersensitive reaction, which is a complex immune response involving T cells and leading to tissue damage or inflammation. This type of hypersensitivity is characterized by a lag phase of 12-24 hours before the onset of symptoms.
**Why the Correct Answer is Right**
The Arthus reaction (a) is a classic example of a delayed type of hypersensitive reaction, occurring when antibodies bind to antigens in the skin, leading to complement activation and tissue damage. Bronchial asthma (b) is often associated with a type IV hypersensitivity reaction, where T cells play a key role in the inflammation and airway constriction seen in this condition. Multiple sclerosis (d) is an autoimmune disease characterized by demyelination, which is thought to result from a delayed type of hypersensitive reaction involving T cells and autoantibodies.
**Why Each Wrong Option is Incorrect**
**Option A:** The Arthus reaction is indeed a type of hypersensitive reaction, but it is typically classified as an immediate or type III hypersensitivity reaction, not a delayed type.
**Option B:** While bronchial asthma can involve a type IV hypersensitivity reaction, it is not the primary mechanism of disease in this condition.
**Option C:** There is no evidence to suggest that multiple sclerosis is a delayed type of hypersensitive reaction. It is an autoimmune disease with a complex pathophysiology.
**Clinical Pearl / High-Yield Fact**
Delayed type hypersensitivity reactions often involve T cells and can lead to tissue damage or inflammation. This type of reaction is typically characterized by a lag phase of 12-24 hours before the onset of symptoms.
**Correct Answer:**
✓ Correct Answer: C. abc