CD28 (Cluster of Differentiation 28) is a homodimeric stimulatory cell surface receptor of the immunoglobulin (Ig) superfamily that is located on the chromosome 2q33.2. It is expressed on naive T cells and has also been found on the surface of plasma cells, eosinophils, and neutrophils. CD28 remains the most extensively studied costimulatory molecular and is a primary one for T-cell activatio. The control of T-cell responses through CD28 co-stimulation provides a means of anti-self and antimicrobial immunity. CD28 is essential for the lymphocyte activation and survival. A number of antigen-experienced T-cells lose CD28, and then can be re-activated without its engagement. Diseases linked to CD28 involve mycosis fungoides and Sezary's disease and the related pathways are Th2 differentiation pathway and RET signaling. EGFR (Epidermal growth factor receptor, also known as ErbB1, ErbB or HER1) is a type I transmembrane glycoprotein involved in normal growth. It belongs to a member of the receptor tyrosine kinase superfamily and makes up the ErbB family with HER2/neu (ErbB-2), HER3 (ErbB-3) and HER4 (ErbB-4). The EGFR gene is encoded on chromosome 7p11.2 and activated by binding to specific protein ligands, such as epidermal growth factor (EGF) and transforming growth factor α (TGF-α). Ligand binding induces EGFR dimerizations resulting in protein-tyrosine kinase activation and cellular signaling. EGFR also plays a role in carcinogenic responses and the increased expression of it in most cases is predictive of tumor progression.