Autologous stem cell transplantation for paediatric‐onset polyarteritis nodosa: changes in autoimmune phenotype in the context of reduced diversity of the T‐ and B‐cell repertoires, and evidence for reversion from the CD45RO+ to RA+ phenotype

We have studied immune reconstitution in a patient with paediatric-onset polyarteritis nodosa treated with high-dose immunosuppressive agents followed by stem cell rescue. The patient developed several new autoimmune phenomena over the 18 months after immunosuppression and stem cell rescue. Flow cytometry, reverse transcription-polymerase chain reaction (RT-PCR) heteroduplex and isotype-specific RT-PCR analysis of immunoglobulin expression showed that the T- and B-cell repertoires were highly restricted in the first few months after treatment. The dominant T-cell clones seen after reconstitution were persistently expanded, were different from those which could be demonstrated before autologous stem cell transplantation, and were in the CD8(+) population. Our data also show that 12 months after treatment these expanded T-cell clones were within the CD45RA(+) population, suggesting that reversion from the CD45RO(+) to the CD45RA(+) phenotype had occurred in vivo.