Immunolocalization of cyclophilin in normal and cyclosporin A-treated human lymphocytes

A polyclonal rabbit antibody against a protein fraction (10-30 kDa) of human thymuses with a high CsA-binding activity of dominant protein cyclophilin (CPH) was prepared and characterized. In immunoblotting with the cell lysate from JURKAT T cell line, this antibody specifically reacted with 18-kDa protein corresponding to CPH. In indirect immunofluorescence the antibody visualized granular structures in JURKAT cells and human peripheral blood lymphocytes. In JURKAT cells cultivated with 1-2 micrograms of CsA per ml for 7 days a much weaker reaction of the antibody was found, compared with non-treated cells. In some CsA-treated cells the antibody visualized various 'star-like' or filamentous structures. A similar staining pattern has also been obtained in lymphocytes of the patients receiving CsA therapy. Complementary staining with rhodamine-tagged phalloidin revealed changes in F-actin distribution of CsA-treated JURKAT cells. In conclusion, the treatment with CsA induces dramatic changes of CPH cellular distribution, which may take part in the final therapeutic effect of the drug.