T regulator lymphocytes (Tregs) play a key role in the maintenance of immune tolerance and in the development of autoimmune diseases. Expression of Foxp3 is specific for Tregs, and can be used for the identification of these cells. This study investigated the variations of Tregs Foxp3+ in the kidney biopsies inflammatory infiltrate of different lupus nephritis classes compared to that of ANCA glomerulonephritis, acute tubulointerstitial nephritis and nephroangiosclerosis. Sections of paraffin-embedded tissue have been stained by immunohistochemistry with anti-CD3 and anti-FoxP3 antibodies. We find that the ratio of FoxP3+/CD3+ cells is significantly lower in patients with lupus nephritis class IV and in patients with vasculitides than in the course of nephroangiosclerosis, tubulointerstitial nephritis and lupus nephritis class V. The data presented herein demonstrate a decrease of FoxP3+ Treg cells in the inflammatory infiltrate of lupus nephritis, particularly during the most active phases of lupus nephritis, as observed in the course of a IV class nephritis.