Use of rapamycin in the induction of tolerogenic dendritic cells

Rapamycin (RAPA), a macrocyclic triene antibiotic pro-drug, is a clinically-utilized 'tolerance-sparing' immunosuppressant that inhibits the activity of T, B, and NK cells. Furthermore, maturation-resistance and tolerogenic properties of dendritic cells (DC) can be supported and preserved by conditioning with RAPA. Propagation of murine bone marrow (BM)-derived myeloid DC (mDC) in clinically relevant concentrations of RAPA (RAPA-DC) generates phenotypically immature DC with low levels of MHC and significantly reduced co-stimulatory molecules (especially CD86), even when exposed to inflammatory stimuli. RAPA-DC are weak stimulators of T cells and induce hyporesponsiveness and apoptosis in allo-reactive T cells. An interesting observation has been that RAPA-DC retain the ability to stimulate and enrich the regulatory T cells (Treg). Presumably as a result of these properties, alloantigen (alloAg)-pulsed recipient-derived DC are effective in subverting anti-allograft immune responses in rodent transplant models, making them an attractive subject for further investigation of their tolerance-promoting potential.