On page 751 Webster et al. show that an antibody-cytokine combination provides prolonged protection for transplanted foreign tissues without long-term immune suppression. The combination could be a step toward new drugs that deflect attacks on transplanted organs but don't increase vulnerability to infection.
Regulatory T (T reg) cells quell immune attacks, thereby helping to tame autoimmune diseases and prevent rejection of transplanted organs. Injections of T reg cells grown in tissue culture can pacify immune reactions in mice, and many researchers are now seeking ways to coax these cells into replicating in vivo. This group and others had previously shown that T reg cell numbers could be boosted by injecting mice with the T cell growth factor interleukin (IL)-2 and an antibody that reacts with it.
Webster et al. now show that a brief treatment with the cytokine-antibody mixture increases the abundance of T reg cells throughout the body. These fresh T reg cells protected mice from developing EAE, a rodent model of multiple sclerosis, by preventing disease-inducing effector T cells from invading the central nervous system.
When the team transplanted diabetic mice with foreign pancreatic β cells, IL-2/antibody treatment prolonged the survival and function of the transplanted cells, even after nearly all of the induced T reg cells had vanished. How the combo treatment prompts long-term tolerance without causing prolonged increases in T reg cell numbers remains a mystery. In the meantime, for the IL-2/antibody combo to eventually make it to the clinic, scientists need to determine whether the treatment has the same effect on human T reg cells.
