CTLA4-Ig Therapy Attenuates Bronchiolitis Obliterans after Mouse Intrapulmonary Trachial Transplantation Model through Possibility of Effect of LAG3+Tregs

Purpose CTLA4-Ig has been used as a treatment for rheumatoid arthritis in clinical practice. CTLA4-Ig was reported to induce lymphocyte-activation gene 3 positive regulatory T cells (LAG3+ Tregs), which produce high amounts of IL-10. This effect on LAG3+Tregs is thought to be one of the mechanisms of the therapeutic effect of CTLA4-Ig in rheumatoid arthritis patients. Recently, CTLA4-Ig was reported to improve long-term outcomes in kidney transplant recipients. We hypothesized that CTLA4-Ig can attenuate chronic lung allograft dysfunction (CLAD) after lung transplantation. The objective of this study was to investigate the effects of CTLA4-Ig therapy in a mouse intrapulmonary tracheal transplantation (IPTT) model, which is an animal model of CLAD. Methods C57BL/6 (B6) mice received IPTT from major-mismatched BALB/c donors. B6 mice were randomly divided into 2 groups. In the CTLA4-Ig group (n = 13) , recipient mice were intraperitoneally injected with 500 µg of CTLA4-Ig immediately after IPTT and on day 7, 14 and 21. In the control group, recipients (n = 11) were injected with 500 µg of human IgG in the same manner. After recipient animals were sacrificed on day 28, Masson's trichrome staining of the extracted left lung and semiquantitative analysis of the graft lumenal obliteration were conducted. Real-time PCR of the lung was performed (another set of groups were made for the analysis; CTLA4-Ig n = 9, control group n = 7). Results The lumenal obliteration ratio in the tracheal allografts was significantly reduced in the CTLA-Ig group (63.0 ± 7.51% vs. 90.1 ± 2.22%, p = 0.004) (Figure A, B). Real-time PCR of the lung revealed that the gene expression ratio of LAG3 to CD4 expression (LAG3/CD4) ratio was significantly upregulated in the CTLA4-Ig group (2.81 ± 0.71 vs. 0.98 ± 0.12, p = 0.041) (Figure C). Conclusion CTLA4-Ig attenuated the fibrous airway obliteration in the mouse IPTT model. CTLA4-Ig may promote LAG3+Treg-mediated anti-inflammatory effects.