CD28 Blockade Bioassay
The CD28 Blockade Bioassays are bioluminescent cell-based assays used to measure the potency and stability of ligands or antibodies that bind and block CD28/B7 family members, CD80 and CD86 (collectively referred to as B7 for this bioassay). CD28 binds to B7 on antigen-presenting cells (APCs). Co-stimulation of T cells by CD28 activation initiates signaling cascades that result in AP-1 and NFkappaB transcription factor activation and nuclear translocation. These pathways significantly enhance T cell cytokine production (specifically, interleukin-2 [IL-2]), which promotes T cell proliferation, differentiation and survival. Blockade of CD28 has proven beneficial in preclinical and clinical studies to reduce autoimmunity and alloimmunity. The CD28 Blockade Bioassay reflects the mechanism of action (MOA) of biologics designed to block the interaction of CD28 with its B7 family ligands.