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. CD44, also known as CD44 antigen, ECMRIII (Extracellular matrix receptor III), HCAM (Homing cell adhesion molecule), Pgp-1 (phagocytic glycoprotein-1), HUTCH-1, etc., is cell surface adhesion receptor and transmembrane glycoprotein in humans encoded by the CD44 gene on the chromosome 11p13. It is a ubiquitous glycoprotein produced throughout the body with a molecular weight of about 85-200 kDa. CD44 contains certain primary domains including the ectodomain, the transmembrane and intracellular domain. It is probably the most well-characterized receptor for hyaluronic acid (HA) and has been reported to be involved in adhesive cell-cell and cell-matrix interactions, cell migration and cell homing. CD44 is also a widely distributed transmembrane adhesion molecule with high expression in cancers.