In 1986, David Khayat went to the Mount Sinaï school medicine in New York (Department of Biochemistry, J.C Unkeless) and got his Ph.D. in tumor immunology in 1988 at the University Pierre and Marie Curie in Paris. During his Ph.D., he has been working on the identification and purification of the soluble Fc receptors both, in mouse and human sera, and set up a new ELISA sandwich assay for the detection and the quantitive dosage of this soluble molecule. He demonstrated the relationship between the release of this soluble receptor in human serum (called also immunoglobuling binding factors IBF) and different pathologic conditions (AIDS, ITP ...).