ABSTRACT
<p><b>BACKGROUND</b>Previous 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.</p><p><b>METHODS</b>Flow 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.</p><p><b>RESULTS</b>M290-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.</p><p><b>CONCLUSION</b>Regardless of the underlying mechanisms, these data document that depletion of CD103-expressing cells represents a viable strategy for therapeutic intervention in islet allograft rejection.</p>