Close association between proteinuria and regulatory T cells in patients with idiopathic nephrotic syndrome.

BACKGROUND

Idiopathic nephrotic syndrome (INS) has been considered to be a T cell disorder. Supporting this hypothesis is the reported occurrence of remission following measles infection, which suppresses T cell function. In contrast, there has been no case report suggesting an association between influenza B virus infection and the remission of INS.

CASE-DIAGNOSIS/TREATMENT: We report the case of a 5-year-old boy with INS who achieved remission without steroid treatment in response to influenza B virus infection. Although he relapsed soon after remission, he was successfully treated with prednisolone. Both the induction of remission and the response to prednisolone were associated with an increase in the number of circulating regulatory T cells (Tregs), assessed as CD4(+)CD25(+)Foxp3(+) cells. These results suggest that both influenza B virus infection and steroid administration increased the number of circulating Tregs, thus leading to the remission of INS.

CONCLUSIONS

In summary, our case indicates an important role for Tregs in the development of the proteinuria associated with INS and sheds light on its pathogenesis. Further studies are warranted.