CD3D and CD3E are components of the T cell receptor signaling complex, confirming T cell lineage identity. CD4 is a surface co-receptor defining the CD4⁺ T cell lineage. CD2 is a surface adhesion molecule broadly expressed on T cells and NK cells, supporting T cell activation. CD40LG (CD40 ligand) is expressed on activated CD4⁺ T cells and is involved in T cell-B cell interactions. Together these markers identify CD4⁺ T cells and distinguish them from CD8⁺ and regulatory T cell populations.
