Yes, CD4 is a protein. More specifically, it's a transmembrane glycoprotein.
What is CD4?
CD4 (cluster of differentiation 4) is a crucial protein found on the surface of certain immune cells, most notably helper T cells. It plays a vital role in the immune system. As a glycoprotein, it contains carbohydrate chains attached to its protein structure.
Several sources confirm CD4's protein nature:
- Wikipedia: Describes CD4 as a "glycoprotein that serves as a co-receptor for the T-cell receptor (TCR)." https://en.wikipedia.org/wiki/CD4
- NCBI Gene Database: States that the gene encodes the "CD4 membrane glycoprotein of T lymphocytes." https://www.ncbi.nlm.nih.gov/gene/920
- UniProt: Identifies CD4 as an "integral membrane glycoprotein" essential for immune responses. https://www.uniprot.org/uniprotkb/P01730/entry
- ScienceDirect: Refers to CD4 as a "membrane glycoprotein receptor expressed on helper T-cells." https://www.sciencedirect.com/topics/immunology-and-microbiology/cd4
- König et al. (1992) and Salter et al. (1990): These studies explicitly identify CD4 and CD8 as transmembrane proteins.
CD4's Function
CD4's primary function is to act as a co-receptor alongside the T-cell receptor (TCR) in activating T cells. This process is crucial for initiating an immune response against pathogens.
- T-cell activation: CD4 binds to MHC class II molecules, facilitating T cell recognition of antigens presented by antigen-presenting cells.
- Thymocyte differentiation: CD4 plays a role in the maturation of T cells in the thymus.
Commercial Availability
The widespread availability of recombinant human CD4 protein from companies like R&D Systems and Sino Biological further supports its established status as a protein used in research and development. https://www.rndsystems.com/products/recombinant-human-cd4-protein-cf_10327-cd, https://www.sinobiological.com/recombinant-proteins/human-cd4-10400-h08h
