Which of the blood cells secrete major basic protein?
**Core Concept**
The major basic protein (MBP) is a type of proteoglycan secreted by a specific type of white blood cell that plays a crucial role in the immune system, particularly in the context of allergic reactions and parasitic infections. This protein is involved in the pathogenesis of certain diseases, including multiple sclerosis and asthma.
**Why the Correct Answer is Right**
The correct answer is a type of white blood cell known as the eosinophil. Eosinophils are a subset of granulocytes that are involved in fighting parasites and in the pathogenesis of allergic reactions. They secrete major basic protein, which is a key mediator in the development of tissue damage and inflammation. The MBP secreted by eosinophils is a 25-kDa protein that has been implicated in the pathogenesis of several diseases, including asthma and multiple sclerosis.
**Why Each Wrong Option is Incorrect**
**Option A:** Neutrophils are another type of white blood cell, but they do not secrete major basic protein.
**Option B:** Lymphocytes are a type of white blood cell involved in the immune response, but they do not secrete MBP.
**Option C:** Monocytes are a type of white blood cell involved in the immune response, but they do not secrete MBP.
**Clinical Pearl / High-Yield Fact**
Eosinophils are often elevated in conditions such as asthma, allergies, and parasitic infections, and the MBP secreted by these cells plays a key role in the pathogenesis of these diseases.
**Correct Answer:** C. Eosinophils.