King's College London

Background: After inflammatory stimulus, mast cells (MC) migrate to secondary lymphoid organs contributing to adaptive immune response. There is growing evidence that MC also contribute to transplant tolerance, but little is known about MC kinetics in the setting of transplant tolerance and rejection. Likewise it has been demonstrated that complement split products, which are known to act as chemoattractants for MC, are necessary for transplant tolerance.

Methods: Naive skin and lymph nodes, skin grafts and draining lymph nodes from wild type and complement deficient mice treated with a tolerogenic protocol were analyzed.

Results: Early after tolerance induction MC leave the graft and migrate to the draining lymph nodes. After this initial efflux, MC reappear in tolerant skin grafts in numbers exceeding that of naive skin. MC density in draining lymph nodes obtained from tolerant mice also increased post transplant. There was no difference in MC density, migration and degranulation status between wild type and complement deficient mice implicating that chemotaxis is not disturbed in complement deficient mice.

Conclusion: This study gives detailed insight in kinetics of MC migration during transplant tolerance induction and rejection providing further evidence for a role of MC in transplant tolerance.