Organ transplantation: modulation of T-cell activation pathways initiated by cell surface receptors to suppress graft rejection

Drug repurposing: Ibrutinib exhibits immunosuppressive potential in organ transplantation

Long-term administration of classic immunosuppressants can induce severe adverse effects. The development of novel immunosuppressants confronts great challenges and opportunities. Ibrutinib, an approved drug for B-cell lineages and chronic graft versus host disease (cGVHD), exhibits immunosuppressive efficacy in autoimmune diseases. Ibrutinib's potential as an immunosuppressant in organ transplantation has not been investigated to date. In a xeno-artery patch model ex vivo, ibrutinib inhibited the proliferation of PBMCs (POD 14-42), mainly CD3⁺CD4⁺ and CD3⁺CD8⁺ T cells ex vivo. The secretion of cytokines (IL-6, IL-2 and IFN-γ) was suppressed in response to ibrutinib. In allo-skin transplantation models, ibrutinib delayed the rejection of grafted skins. Ibrutinib decreased the amount of T/B cells and lymphocyte infiltration. Altogether, ibrutinib exhibited immunosuppressive potential through cytokine regulation and T cell inhibition ex vivo and in vitro. Repositioning of ibrutinib as an immunosuppressant will greatly facilitate novel immunosuppressant development.

Caerulomycin A suppresses immunity by inhibiting T cell activity

BACKGROUND

Caerulomycin A (CaeA) is a known antifungal and antibiotic agent. Further, CaeA is reported to induce the expansion of regulatory T cell and prolongs the survival of skin allografts in mouse model of transplantation. In the current study, CaeA was purified and characterized from a novel species of actinomycetes, Actinoalloteichus spitiensis. The CaeA was identified for its novel immunosuppressive property by inhibiting in vitro and in vivo function of T cells.

METHODS

Isolation, purification and characterization of CaeA were performed using High Performance Flash Chromatography (HPFC), NMR and mass spectrometry techniques. In vitro and in vivo T cell studies were conducted in mice using flowcytometry, ELISA and thymidine-[methyl-(3)H] incorporation.

RESULTS

CaeA significantly suppressed T cell activation and IFN-γ secretion. Further, it inhibited the T cells function at G1 phase of cell cycle. No apoptosis was noticed by CaeA at a concentration responsible for inducing T cell retardation. Furthermore, the change in the function of B cells but not macrophages was observed. The CaeA as well exhibited substantial inhibitory activity in vivo.

CONCLUSION

This study describes for the first time novel in vitro and in vivo immunosuppressive function of CaeA on T cells and B cells. CaeA has enough potential to act as a future immunosuppressive drug.