Apoptosis or programmed cell death is one of the regulation mechanisms of cell homeostasis.

Fas is a transmembrane receptor protein which transmits a cell death signal when cross linked with an antibody or with its physiological ligand—Fas ligand (Fas L).1 Fas and Fas L have a pivotal role in regulating lymphocyte apoptosis and maintaining lymphocyte homeostasis.

Soluble forms of Fas and Fas L may be detectable and measured in the serum,2 and may reflect the activation of this pathway. Moreover, soluble forms of Fas regulate Fas/Fas L mediated apoptosis.3 Raised levels of soluble Fas (sFas) have been shown in various chronic inflammatory rheumatic diseases, systemic lupus erythematosus, Sjögren's syndrome,1 ,4 ,5 and in the synovial fluid of rheumatoid arthritis.6 These diseases are …