Visualizing the innate and adaptive immune responses underlying allograft rejection by two-photon microscopy

Area of Science:

• Immunology
• Transplantation Biology
• Cellular and Molecular Medicine

Background:

• Transplant rejection is a complex process involving both innate and adaptive immunity.
• Understanding the roles of donor and host cells is crucial for managing rejection.
• Current models lack the resolution to visualize these dynamic cellular interactions in real-time.

Purpose of the Study:

• To investigate the dynamic cellular mechanisms of transplant rejection using intravital imaging.
• To elucidate the contributions of donor and host cells in the rejection process.
• To define the pathways of antigen presentation and T cell activation in allograft rejection.

Main Methods:

• Development of a novel ear skin graft model compatible with intravital imaging.
• Tracking of donor and host cell migration and interaction within the graft.
• Analysis of T cell priming, trafficking, and targeting of graft cells.

Main Results:

• Donor dermal dendritic cells (DCs) rapidly emigrated from the graft.
• Host CD11b(+) mononuclear cells infiltrated the graft, captured donor antigens, and migrated to lymph nodes.
• Graft-reactive CD8(+) T cells were cross-primed, entered the graft, and selectively targeted graft cells, particularly at the dermis-epidermis junction.

Conclusions:

• The study reveals a stepwise progression of CD8(+) T cell activity during allograft rejection.
• Insights into antigen presentation and T cell targeting provide a framework for evaluating immunotherapies.
• Targeting key steps in T cell-mediated rejection could offer new therapeutic strategies.