Anti-Mouse CD28 [Clone E18] - FITC (C2473-GRP)

CD28 is a 44 kD glycoprotein and member of the Ig superfamily that produces co-stimulatory signals necessary for T cell activation and survival as part of the B7-1/B7-2–CD28/CTLA-4 pathway1. The two B7 family proteins, B7-1 (CD80) and B7-2 (CD86), have dual specificity for the stimulatory receptor CD28 and the inhibitory receptor CTLA-4 (CD152). When B7-1 and B7-2 interact with CD28, an important co-stimulatory signal, transmitted via CD28, synergizes with the TCR signal to regulate the threshold for T cell activation and promote T cell survival, clonal expansion, and differentiation. CD28 also promotes interleukin-2 (IL-2) production. In contrast, when B7-1 and B7-2 engage with CTLA-4, a negative signal inhibits TCR- and CD28- mediated signaling as well as IL-2 synthesis, and the T-cell response is terminated. E18 was generated by alternately immunizing CD28-/- mice with A20 cells expressing mCD28 and recombinant mCD28Ig2. Splenic cells were fused with X63Ag8.653 for hybridoma production. E18 completely blocks CD28 ligation by B7 molecules3. Additionally, E18 enhances anti-CD3-induced proliferation of peripheral T cells. In vivo, E18 acts as an inhibitor of CD28 signaling and causes a reversible reduction in Treg cell frequencies among CD4+ cells.