Which of the following is Pan leukocyte marker
**Core Concept**
A pan-leukocyte marker is a type of antibody that recognizes and binds to a specific protein or antigen present on the surface of all types of white blood cells, including lymphocytes, monocytes, neutrophils, and eosinophils. These markers are essential for identifying and diagnosing various hematological disorders.
**Why the Correct Answer is Right**
The correct answer is CD45, also known as leucocyte common antigen (LCA). CD45 is a transmembrane glycoprotein that is expressed on the surface of all leukocytes and plays a crucial role in the regulation of T-cell receptor signaling. It is involved in the activation, proliferation, and differentiation of T-cells, and its expression is essential for the proper functioning of the immune system.
**Why Each Wrong Option is Incorrect**
* **Option A:** CD1 is a type of glycoprotein that is primarily expressed on the surface of antigen-presenting cells, such as dendritic cells and macrophages, and is involved in the presentation of lipid antigens to T-cells.
* **Option B:** CD3 is a component of the T-cell receptor complex and is expressed on the surface of mature T-cells, but it is not a pan-leukocyte marker.
* **Option D:** CD68 is a marker for monocytes and macrophages, but it is not expressed on all types of leukocytes.
**Clinical Pearl / High-Yield Fact**
CD45 is a crucial marker in the diagnosis of acute lymphoblastic leukemia (ALL), and its expression is often used to distinguish ALL from acute myeloid leukemia (AML).
**Correct Answer:** B. CD3 is a component of the T-cell receptor complex and is expressed on the surface of mature T-cells, but it is not a pan-leukocyte marker.