| Further Information: | B7-1/CD80 and B7-2/CD86, together with their receptors CD28 and CTLA-4, constitute one of the dominant co-stimulatory pathways that regulate T-�and B-cell responses . Although both CTLA-4 and CD28 can bind to the same ligands, CTLA-4 binds to B7-1 and B7-2 with a 20-100�fold higher affinity than CD28 and is involved in the down-regulation of the immune response . Mature mouse B7-1 consists of a 209�amino acid (aa) extracellular domain (ECD) with two immunoglobulin-like domains, a 22�aa transmembrane segment, and a 38�aa cytoplasmic domain . Within the ECD, mouse B7-1 shares 50%�and 68%�aa sequence identity with human and rat B7-1, respectively. Alternative splicing generates a short isoform that lacks the second Ig-like domain but retains the ability to bind CD28 . Both human and mouse B7-1 and B7-2 can bind to either human or mouse CD28 and CTLA-4 . B7-1 is expressed on activated B�cells, activated T�cells, and macrophages. B7-2 is constitutively expressed on interdigitating dendritic cells, Langerhans cells, peripheral blood dendritic cells, memory B�cells, and germinal center B�cells. |
