This suggests that the anti-BTLA reagent needs to be in close contact with, if not immediately juxtaposed to the stimulus that causes the T cells to proliferate. Figure 5 shows a schematic illustrating a possible mechanistic explanation for this observation. In Fig. 5a, bead-absorbed anti-CD3ε clusters and activates the TCR and the cell proliferates. Anti-BTLA reagents on the same bead can localize BTLA to synapse, bringing the BTLA molecule in juxtaposition to the TCR. This allows the activation of BTLA to recruit the AZD6738 supplier SHP-2 phosphatase adjacent

to the intracellular domain of the TCR, resulting in dephosphorylation of the TCR complex and countering T cell proliferation. In Fig. 5b, bead-absorbed anti-CD3ε clusters and activates the TCR and the cell proliferates. An anti-BTLA reagent on a different bead is dislocated physically from the immunological synapse and

is unable to localize BTLA to the synapse. Hence, the SHP-2 phosphatase cannot be recruited adjacent to the intracellular domain of the TCR and T cell proliferation is unaffected. We propose a model whereby Fig. Selleck Palbociclib 5a is analogous to the presence of a cross-linking reagent when the reagents are directly immobilized on the plate. When the cross-linking reagent is used, it brings the stimulus and the anti-BTLA reagent into close physical proximity as they interact and T cell proliferation is inhibited, as shown in Fig. 1b. Without a cross-linking reagent, the stimulus and the anti-BTLA reagent are immobilized

directly on the plate and dislocated physically from each other and T cell proliferation is unaffected, as shown in Fig. 1a. This proposed mechanism of action of an anti-proliferative BTLA-specific reagent is plausible based on the association of BTLA with elements of the TCR signalling complex [1,5,30]. It is also consistent 4-Aminobutyrate aminotransferase with functional observations described in the literature. Hurchla et al. [2,4] and Sedy et al. [9] demonstrated that HVEM signals through BTLA by co-culturing Chinese hamster ovary (CHO) cells expressing the IAd major histocompatibility complex (MHC) molecule and also expressing either mBTLA or mHVEM with OVA antigen-activated CD4+ DO11.10 cells [2,4,9]. Co-expression of mBTLA had no effect on lymphocyte proliferation and co-expression of mHVEM inhibited lymphocyte proliferation significantly. This HVEM-mediated inhibition of proliferation did not occur if the CD4+ DO11.10 cells were from a BTLA knock-out mouse. In this system, the use of BTLA expressed on the surface of transfected cells is analogous to the use of the beads-based system. It is possible that the anti-BTLA reagent (in this case the HVEM ligand) needs to be juxtaposed similarly to the stimulus causing target cell proliferation (in this case the IAd MHC molecule presenting the OVA antigen). In a more reduced in vitro proliferation system, Gonzalez et al.