Cyclosporine inhibits class II major histocompatibility antigen presentation by xenogeneic endothelial cells to human T lymphocytes by altering expression of the class II transcriptional activator gene.
BACKGROUND
Cyclosporine (CsA) is currently given to recipients of vascularized xenografts as part of the immunosuppressive regimen required to prevent the hyperacute rejection phase. The effects of CsA on non-lymphoid immune cells, such as endothelial cells (ECs), have not been well characterized and sometimes seem contradictory, because both protective and adverse effects have been reported. In the present study, we investigated in vitro whether CsA could alter the antigenicity of activated porcine aortic endothelial cells (PAECs) by reducing class I and class II MHC antigen expression.


METHODS
The effect of CsA on MHC antigen expression during tumor necrosis factor (TNF)-alpha- or lymphocyte-mediated PAEC activation was evaluated in vitro by flow cytometry and correlated to the ability of porcine ECs to promote human T lymphocyte proliferation. The effect of CsA on class II MHC antigen mRNA expression was also analyzed and related to class II transcriptional activator (CIITA) mRNA expression.


RESULTS
Flow cytometry analysis showed that TNF-alpha-mediated induction of class II MHC antigen expression on PAECs was completely inhibited by CsA, whereas expression of class I MHC was reduced by 50%. The inhibition was dose dependent (at drug concentrations ranging from 2.5 microg/ml to 20.0 microg/ml) and was consistently observed at all time points (24-72 hr) during the activation period. Decreased MHC antigen expression dramatically reduced the ability of PAECs to further promote human T-cell proliferation. Similar levels of inhibition were achieved using an anti-porcine class II MHC blocking monoclonal antibody. Pretreatment of PAECs with CsA for 4 hr before coculture with human peripheral blood leukocytes efficiently blocked the induction on PAECs of E-selectin and class II MHC antigens and inhibited overexpression of class I antigens. Semiquantitative reverse transcriptase-polymerase chain reaction experiments showed that CsA markedly reduced the steady-state level of porcine class II (SLA-DRA and SLA-DQA) mRNA at 16 hr, compared with PAECs stimulated with TNF-alpha alone. The reduced level of class II MHC mRNA was associated with a lack of CIITA expression at this time point, suggesting that CsA could alter transcription or promote the rapid decay of CIITA mRNA.


CONCLUSIONS
Our study indicates that CsA could play a role in preventing porcine MHC antigens being directly presented to human T lymphocytes by xenogeneic ECs.
Charreau
B
B
INSERM U437, Institut de Transplantation et de Recherche en Transplantation, C.H.U. de Nantes, France.
Coupel
S
S
Boulday
G
G
Soulillou
J P
JP
D000818:Animals; D000938:Antigen-Presenting Cells; D001011:Aorta / Q000166:cytology; D018920:Coculture Techniques; D016572:Cyclosporine / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects / Q000276:immunology; D004730:Endothelium, Vascular / Q000166:cytology* / Q000276:immunology*; D015870:Gene Expression; D005802:Genes, MHC Class II / Q000235:genetics*; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006801:Humans; D012333:RNA, Messenger / Q000378:metabolism; D013552:Swine; D015534:Trans-Activators / Q000235:genetics; D014158:Transcription, Genetic
D000949:Histocompatibility Antigens Class II; D012333:RNA, Messenger; D015534:Trans-Activators; D016572:Cyclosporine