Description
CTLA-4 is expressed in low copy number by T-cells only after activation, but it binds CD28-ligand with approximately 20-fold higher affinity than CD28. A soluble form of the extracellular domain of CTLA-4 has been shown to bind CD28-ligand with high avidity and to suppress T-cell-dependent antibody responses in vivo. Large doses of this soluble protein also suppress responses to a second immunization