Antithymocyte globulin impairs T-cell/antigen-presenting cell interaction: disruption of immunological synapse and conjugate formation.

Antithymocyte globulin (ATG) is employed for the treatment and prevention of acute organ rejection after transplantation. However, the mechanisms underlying its immunomodulatory capacities beyond cellular depletion remains ill defined. A stable interaction between T-cells and professional antigen-presenting cells (APC) and full T-cell stimulation requires a complex molecular rearrangement at the T-cell/APC interface, the so called immunological synapse. Here we investigated, whether ATG affects T-cell/APC interactions. ATG concentration and time-dependently inhibited relocalization of the T-cell receptor/CD3 complex as well as adhesion molecules and cytoskeletal proteins of human peripheral blood T-cells and a human T-cell line towards the APC contact site. Moreover, ATG-treated peripheral blood T-cells were incapable to form conjugates with APCs. In conclusion, ATG impairs T-cell/APC conjugate formation, a mechanism that may help to understand the functional inactivation of peripheral blood T-cells that have escaped cellular depletion after ATG treatment.