Effects of cyclosporin A treatment on clinical course and inflammatory cell apoptosis in experimental autoimmune encephalomyelitis induced in Lewis rats by inoculation with myelin basic protein.

Experimental autoimmune encephalomyelitis (EAE) was induced in Lewis rats by inoculation with myelin basic protein (MBP) and adjuvants. Rats were treated with second daily injections of saline or cyclosporin A (CsA) from the day of inoculation. Saline-treated rats had an acute episode of disease followed by clinical recovery. Rats treated with CsA 16 or 32 mg/kg had minimal signs of EAE at the usual time after inoculation, but developed signs of disease after treatment was ceased. Rats treated with CsA 8 mg/kg had a delayed first episode of disease and then developed a relapsing or a chronic persistent course of disease. CsA 4 mg/kg delayed the onset of disease. To study the effects of CsA on the inflammatory infiltrate, cells were extracted from the spinal cords of rats with EAE, 16 h after a single injection of CsA or saline. Extracted cells were labelled with antibodies to T cells, CD11b/c (macrophages/microglia), CD95 (Fas) and Fas ligand. CsA 4 mg/kg did not alter the composition of the inflammatory infiltrate. Treatment with higher single doses of CsA caused a dose-dependent decline in the percentage of T cell receptor (TCR) alphabeta+ cells in the inflammatory infiltrate. All doses of CsA caused a significant increase in the number and percentage of cells that were apoptotic. CsA treatment caused an increase in the percentages of CD5+ and TCR alphabeta+ cells that were apoptotic. There was a decline in the percentage of apoptotic T cells that were Vbeta8.2+, compared to the percentage of non-apoptotic T cells that were Vbeta8.2+, in CsA treated rats compared to saline-treated controls. This suggests that, while CsA treatment caused a non-specific increase in the overall level of T cell apoptosis in the spinal cord, it abrogated the selective apoptosis of Vbeta8.2+ encephalitogenic T cells that normally occurs during spontaneous recovery from acute EAE.