BACKGROUND:Multiple sclerosis (MS) is often considered to be a CD4, T cell-mediated disease. This is largely based on the capacity of CD4 T cells to induce relapsing experimental autoimmune encephalomyelitis (EAE) in rodents. However, CD4-depletion using a monoclonal antibody was considered unsuccessful and relapsing MS responds well to B cell depletion via CD20 B cell depleting antibodies. The influence of CD20 B cell depletion in relapsing EAE was assessed. METHODS:Relapsing EAE was induced in Biozzi ABH mice. These were treated with CD20-specific (18B12) antibody and the influence on CD45RA-B220 B cell depletion and clinical course was analysed. RESULTS:Relapsing EAE in Biozzi ABH failed to respond to the marked B cell depletion induced with a CD20-specific antibody. In contrast to CD20 and CD8-specific antibodies, CD4 T cell depletion inhibited EAE. CONCLUSION:Spinal cord antigen-induced disease in ABH mice is CD4 T cell-dependent. The lack of influence of CD20 B cell depletion in relapsing EAE, coupled with the relatively marginal and inconsistent results obtained in other mouse studies, suggests that rodents may have limited value in understanding the mechanism occurring following CD20 B cell depletion in humans.