BACKGROUNDPrevious studies using knockout mice document a key role for the integrin CD103 in promoting organ allograft rejection and graft-versus-host disease. However, a determination of whether blockade of the CD103 pathway represents a viable therapeutic strategy for intervention in these processes has proven problematic due to the lack of reagents that efficiently deplete CD103(+) cells from wild type hosts. To circumvent this problem, in the present study, we invented an anti-CD103 immunotoxin (M290-SAP). We investigated whether M290-SAP has capacity to eliminate CD103-expressing cells in vivo and protect transplanted islets from destroying by host immune cells.

METHODSFlow cytometry was used to analyze the efficacy of M290-SAP in depleting CD103-expressing cells in vivo. Then using allogenic islet transplantation models as well as NOD mice with recent onset type 1 diabetes, the therapeutic efficacy of CD103-expressing cell depletion was addressed.

RESULTSM290-SAP dramatically reduces the frequency and absolute numbers of CD103-expressing leukocytes in peripheral lymphatic tissues of treated mice. Balb/c islets transplanted into streptozotocin-induced diabetic C57BL/6 mice under single M290-SAP treatment showed an indefinite survival time compared with untreated mice, M290-treated mice and IgG-SAP treated mice (mean survival time, > 100 days vs. < 20 days). C57BL/6 islets transplanted into hyperglycemic NOD mice under single M290-SAP treatment showed a pronounced delay in allograft rejection compared with untreated mice (mean survival time 12 - 13 days vs. < 7 days). Immunological analysis of mice with long-term islet allograft survival revealed an obvious atrophy thymus and severe downregulation of alloimmunity of CD8 subpopulation response to allogenic stimulation.

CONCLUSIONRegardless of the underlying mechanisms, these data document that depletion of CD103-expressing cells represents a viable strategy for therapeutic intervention in islet allograft rejection.