CD4 is a protein, specifically a cell surface glycoprotein.
Understanding CD4
Based on the provided reference, CD4 is identified as a cell surface glycoprotein. This means that:
- It is a type of protein.
- It has sugar molecules attached to it (hence "glyco-").
- It is found on the outer surface of certain cells.
Therefore, CD4 itself is not a cell, but rather a molecule (a protein) that is present on the surface of some cells.
Key Characteristics from the Reference:
- Nature: Cell surface glycoprotein
- Location: Found on the surface of cells
- Function Highlighted: Binds to a monomorphic region of MHC class II molecules, helping to stabilize the interaction between a T cell receptor (TCR) and MHC class II. This interaction is crucial for immune responses.
In summary, while CD4 is associated with specific cells (like a key found on a door), it is the molecular structure (the key itself - the protein) and not the entire cell (the door).
