ACCELERATED REJECTION OF VASCULARIZED COMPOSITE TISSUE ALLOGRAFTS IN SENSITIZED RECIPIENTS IS CELLULAR-MEDIATED, NOT ANTI-DONOR ANTIBODY-MEDIATED

Hong Xu¹, Shengli Wu¹, Bo Chen¹, Yujie Wen¹, Olayemi Ikusika¹, Hong Zhao¹, Suzanne Ildstad¹.

¹Institute for Cellular Therapeutics, University of Louisville, Louisville, KY, USA.

Presensitization to donor alloantigens results in hyperacute rejection of renal allografts. Currently, the cross-matching process for vascularized composite tissue allotransplantation (VCTA) closely follows the standard practices for solid organ transplantation. However, the role of sensitization in VCTA has not been addressed. Here, MHC-mismatched ACI donors and WF recipients were used to determine the role of sensitization in VCTA. WF rats were presensitized to ACI antigens by skin transplantation with confirmed anti-donor antibody generation. Sensitized WF rats rejected VCTA grafts from ACI rats significantly faster than unsensitized rats, but not hyperacutely. In contrast, ACI kidneys were hyperacutely rejected within 30 minutes by sensitized recipients. In order to define the role of antibody in rejection of VCTA and kidney, naïve WF rats received adoptive transfer of serum from sensitized WF. The rejection time of ACI VCTA (MST 7.8±3.3 days) in adoptively transferred recipients was significantly shorter compared with rejection in sensitized recipients (3.8±0.8 days, P<0.05), but there was no significant difference compared with unsensitized recipients (9.2±3.6 days, P>0.05). When adoptive transferred recipients received ACI kidneys, the renal allografts were hyperacutely rejected within 30 minutes, which was similar to skin sensitized recipients. These results suggest that Ab-mediated rejection represents one predominant barrier for allo-kidney transplantation in sensitized recipients. To further study the mechanism of CTA rejection in sensitized rats, H&E staining was performed on sections of VCTA or kidney tissues at the time of rejection. It demonstrated a moderate infiltration of the dermal stroma by numerous mononuclear cells and destruction of architecture in acceleratedly rejected skin. An extensive infiltration of mononuclear lymphatic cells in acceleratedly rejected muscle was also noted. However, skin or muscle samples of naïve or acceptor rats were devoid of infiltration. Immunofluorescence analysis of antibody deposition was performed. Hyperacutely rejected kidney demonstrated obvious IgG deposition. In contrast, IgG staining was not observed in acceleratedly rejected rat skin and muscle. These results suggest that accelerated rejection of VCTA in sensitized recipients is predominantly cellular-mediated and differs mechanistically from that for renal transplants.