Which of the following surface glycoproteins is most often expressed in human hematopoietic stem cell –
**Core Concept**
Human hematopoietic stem cells (HSCs) express specific surface glycoproteins that help identify and isolate them for research and clinical applications. These surface glycoproteins play a crucial role in the self-renewal, proliferation, and differentiation of HSCs.
**Why the Correct Answer is Right**
CD34 is the most commonly expressed surface glycoprotein on human HSCs. It is a transmembrane phosphoglycoprotein that acts as a cell adhesion molecule, facilitating the interaction of HSCs with other cells and the extracellular matrix. CD34 is also involved in the regulation of HSC proliferation, differentiation, and migration. The expression of CD34 on HSCs is a critical marker for their identification and isolation from other cell populations in the bone marrow.
**Why Each Wrong Option is Incorrect**
**Option A:** CD45 is a transmembrane glycoprotein that is primarily expressed on leukocytes, including T cells, B cells, and macrophages. While CD45 is involved in the regulation of leukocyte signaling and activation, it is not a specific marker for HSCs.
**Option B:** CD14 is a surface glycoprotein that is primarily expressed on monocytes and macrophages, where it acts as a receptor for bacterial lipopolysaccharides. CD14 is not a specific marker for HSCs.
**Option C:** CD19 is a surface glycoprotein that is primarily expressed on B cells, where it plays a critical role in B cell development and activation. CD19 is not a specific marker for HSCs.
**Clinical Pearl / High-Yield Fact**
The expression of CD34 on HSCs is a critical marker for their identification and isolation from other cell populations in the bone marrow. This knowledge is essential for the development of stem cell therapies for various diseases, including leukemia, lymphoma, and autoimmune disorders.
**Correct Answer:** C. CD34.