A role for the B-cell CD74/macrophage migration inhibitory factor pathway in the immunomodulation of systemic lupus erythematosus by a therapeutic tolerogenic peptide.

Systemic lupus erythematosus (SLE) is an autoimmune disease that involves dysregulation of B and T cells. A tolerogenic peptide, designated hCDR1, ameliorates disease manifestations in SLE-afflicted mice. In the present study, the effect of treatment with hCDR1 on the CD74/macrophage migration inhibitory factor (MIF) pathway was studied. We report here that B lymphocytes from SLE-afflicted mice express relatively elevated levels of CD74, compared with B cells from healthy mice. CD74 is a receptor found in complex with CD44, and it binds the pro-inflammatory cytokine MIF. The latter components were also up-regulated in B cells from the diseased mice, and treatment with hCDR1 resulted in their down-regulation and in reduced B-cell survival. Furthermore, up-regulation of CD74 and CD44 expression was detected in brain hippocampi and kidneys, two target organs in SLE. Treatment with hCDR1 diminished the expression of those molecules to the levels determined for young healthy mice. These results suggest that the CD74/MIF pathway plays an important role in lupus pathology.