Stem cells show positivity with
**Core Concept**
Stem cells are undifferentiated cells that have the ability to differentiate into various cell types. They are characterized by their ability to self-renew and differentiate into multiple cell lineages. The identification of stem cells is crucial in various fields, including regenerative medicine and tissue engineering.
**Why the Correct Answer is Right**
Stem cells express specific markers that allow for their identification and isolation. One of the key markers that stain positively in stem cells is **CD34**. CD34 is a transmembrane glycoprotein that is expressed on the surface of hematopoietic stem cells and some other types of stem cells. It plays a crucial role in the adhesion of stem cells to the endothelial cells of blood vessels, allowing them to migrate and colonize new tissues.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because **CD45** is a marker that stains positively in mature leukocytes, not stem cells.
* **Option B:** This option is incorrect because **CD31** is a marker that stains positively in endothelial cells, not stem cells.
* **Option C:** This option is incorrect because **CD68** is a marker that stains positively in macrophages, not stem cells.
**Clinical Pearl / High-Yield Fact**
CD34+ cells are often used as a source of hematopoietic stem cells for transplantation in patients with hematological malignancies.
**Correct Answer:** C. CD34.