Objectives: 

Neuromyelitis optica (NMO) is a severe autoimmune inflammatory disease of the central nervous system (CNS) that mainly affects the spinal cord and optic nerves. The presence of auto antibodies against AQP4 (NMO-IgG or AQP4-Abs) in serum's patients with NMO have significantly improve the diagnosis of the disease and allow critical distinction of this pathology from multiple sclerosis.

Materials: 

Here we present a simple method for detection of AQP4-Abs by which the serum of patients is used as the primary antibody in an immunofluorescence assay performed over HEK cells stably or transiently transfected with hM23-AQP4 C-terminally EGFP tagged. After 24h of transfection cells were fixed, permeabilized and blocked with FCS and BSA. Two protocols were compared one in which the primary antibody was added immediately after the blocking step follow by the regular washing steps and incubation with the secondary Ab, and other in which cells were kept frozen for variable time in blocking solution plus 10 %DMSO before adding the primary Ab. We have analyzed a total of 68 patient's serum diagnose either as NMO (8), multiple sclerosis (36), neuritis optica (4), longitudinally extensive myelitis (6), recurrent myelitis (2), undiagnosed (7), and healthy donors (5).

Results: 

Qualitative analysis by fluorescence microscopy revealed similar results from both protocols, and quantification of fluorescence signal with the image-J software confirm comparable values in both. Our method for detection of NMO-IgG revealed the presence of anti-AQP4 Abs in the total of serums from patients clinically diagnosed as NMO and the absence of it in all the rest of serums analyzed.

Conclusions: 

The possibility to keep frozen slices ready to incubate with the serum of a patient allow us to have the NMO-IgG detection result just in one day of analysis.