Ph.D. Thesis Defense by Ping Li
Monday, July 12, 1999

(Dr. Cheng Zhu, advisor)

"Investigation of the Binding Characteristics and The Possible Blockade of CD16A Molecule"

Abstract

CD16, the most abundant Fc gamma receptor (Fc?R), protects human body from bacterial and virus infection. On the other hand, it triggers immune attacks against host itself in auto-immune diseases and helps IgG opsonized virus to infect leukocytes. The goal of the research presented here is to better understand this immunologically important molecule and explore the possibility of blocking its functions under pathological conditions.

To study CD16 molecule, mammalian cells were transfected to express high level of CD16a as the only Fc?R. The obtained cell line provided an excellent molecular system to investigate the role of CD16a. The very important information of the binding characteristics of CD16a molecule, the kinetics, was obtained by SPR measurement. CD16a was found to dissociate from soluble monomeric IgG ligands with slow off-rates (half-life in the order of minutes).

The question of how to block CD16 and other Fc?Rs under pathological conditions was addressed in two directions. CD16a was made soluble by molecular biology technique. The soluble CD16a molecule has the therapeutic potential to treat auto-immune diseases such as ITP and antibody dependent enhancement of virus such as HIV. To determine the dosage of soluble competitor, the inhibition of Fc?Rs-expressing leukocytes binding to immobilized IgG ligands by both similar and dissimilar competitors was simulated in a modified centrifugation assay. A proposed mathematical model did not only account for the experimental data in CD16 system, but was also generic enough to help the rational design of other receptor based competitive inhibition therapy.