Autoantibody to a novel neuronal antigen in systemic lupus erythematosus and in normal human sera.

A non-Fc receptor-bearing mouse neuroblastoma cell line, Neuro-2a, was used in indirect immunofluorescence tests to characterize the pattern of anti-neuronal activity of human sera in 41 cases of systemic lupus erythematosus (SLE), including seven cases of cerebral lupus, 30 "disease controls" (rheumatoid arthritis and chronic active hepatitis) and 30 healthy subjects. The immunofluorescence reaction with Neuro-2a gave a uniform ring fluorescence of the cell surface of cultured cells at 4 and at 37 degrees C, clusters were seen at 5 to 10 min and surface globules at 20 to 120 min. Titres of antibody to Neuro-2a in SLE ranged from less than 5 (seven cases), 5 to 20 (23 cases) and greater than or equal to 40 (11 cases). Titres of 80 to 160 were given by five of seven cases of cerebral lupus and two of 34 cases without cerebral lupus. Antibody to Neuro-2a was demonstrable in subjects without SLE, but to lower titres (less than 5-20). Of 11 SLE sera with antibody titres greater than or equal to 1:40, the antibody class was IgM in eight, IgG in two and both IgM and IgG in one. Absorption studies indicated that serum reactivity against Neuro-2a cells could be removed from some SLE sera with the cultured human neuroblastoma cell line, SK-N-SH, but not with mouse fibroblasts, mouse 3T3 cells, rat C6 glioma cells, rat transformed mesenchymal cells, nor by homogenates of mouse brain, heart, liver of kidney. Detection of antibody to Neuro-2a cell may be helpful in identifying patients with cerebral disease due to SLE.