 CD80 can be found on the surface of various immune cells including B cells, monocytes and antigen-presenting cells (APCs) such as dendritic cells and is the receptor for the proteins CD28 (for autoregulation and intercellular association) and CTLA-4 (for attenuation of regulation and cellular disassociation) found on the surface of T-cells.CD80 binds to CD28 and CTLA-4 with lower affinity and fast binding kinetics (Kd =4 μM), allowing for quick interactions between the communicating cells.This interaction results in an important costimulatory signal in the immunological synapse between antigen-presenting cells, B-cells, dendritic cells and T-cells that result in T and B-cell activation, proliferation and differentiation.