CTLA-4: A negative regulator of autoimmune disease

CTLA-4, a CD28 homologue expressed on activated cells, binds with high affinity to the CD28 ligand, B and-1 (CD80) and B7-2 (CD86). This study was designed to examine the role of CTLA-4 in regulating autoimmune disease. Murine relapsing-remitting experimental autoimmune encephalomyelitis (R-EAE) is a demyelinating disease mediated by PLP139-161-specific CD4⁺ T cells in SJL/J mice. Anti-CTLA-4 mAbs (or their F(ab) fragments) enhanced in vitro proliferation and pro-inflammatory cytokine production by PLP139-151-primed lymph node cells. Addition of either reagent to in vitro activation cultures potentiated the ability of T cells to adoptively transfer disease to naive recipients. In vitro administration of anti-CTLA-4 mAb to recipients of PLP139-151-specific cells resulted in accelerated and exacerbated disease. Finally, anti-CTLA-4 treatment of mice during disease remission resulted in the exacerbation of relapses. Collectively, these results suggest that CTLA- 4 mediates the downregulation of ongoing immune responses and plays a major role in regulating autoimmunity.