Despite these findings, Boyman noted, no one yet knows why these antibody-cytokine complexes are such potent immune response boosters in vivo.
"A few studies have suggested that injecting a cytokine together with the right antibody increases the half-life of the cytokine in vivo, accompanied by a very mild immune activation," he said. "But our study suggests a different mechanism and that joining a cytokine to its specific antibody opens the way for selective and vigorous stimulation of T cell subsets. With some types of antibodies, injecting IL-2/IL-2 mAb complexes might be clinically useful for tumor immunotherapy and for expanding T cell numbers after bone marrow transplantation. On the other hand, expansion of CD4+ T regulatory cells by IL-2 combined with another type of IL-2 mAb might provide a basis for treating autoimmune disease."