Expression of TGFβ1 and Its Signaling Components by Peripheral Lymphocytes in Systemic Lupus Erythematosus

Transforming growth factor β1 (TGFβ1) is an important immunosuppressive cytokine. Defects in its production by lymphocytes and the failure of TGFβ1 to regulate immunological functions have been described in SLE. Expression of TGFβ1 and the related signaling pathway was studied in the peripheral lymphocytes of SLE patients. The total plasma TGFβ1 level in active and inactive SLE patients compared to healthy controls was also measured. TGFβ1 and all downstream signaling elements were expressed in normal cells. However, in more than 50% of SLE patients the isolated T cell population showed no TGFβ1 mRNA expression and at least one member of the TGFβ1 pathway was also missing (TGFβ-RI, Smad2 and Smad3) in more than half of the patients. Total plasma TGFβ1 level was increased in both active and inactive SLE groups compared to normal controls ( p < 0.05). These data raise questions about the availability of TGFβ1 signaling in lymphocytes in SLE patients, however, the elevated total plasma TGFβ1 level suggests that the failure of TGFβ1 effects is not the consequence of low level of this cytokine in SLE.