AQP4 and myeloid sarcoma: The description of anti-KIR4.1 antibodies was a potential landmark discovery[33], first, because KIR4.1 was observed to co-localize with aquaporin-4 in the brain and represented a plausible antigen[34] and, second, because it provided the first solid evidence that disease-specific autoantibodies could be found in a substantial proportion of adult MS patients[10].