Anti-neurofilament antibodies in the sera of patients with small cell carcinoma of the lung and with visual paraneoplastic syndrome.

The sera of patients with small cell carcinoma of the lung (SCCL) and an associated visual paraneoplastic syndrome (VPNS) have high titer immunoglobulins that react with retinal ganglion cells and with cloned lines of the SCCL. The immunoglobulins in the sera of two patients with SCCL and VPNS reacted with at least one common antigen shared by neural cells and cloned lines of the SCCL. The molecular weights of the predominant neural and tumor antigens were 205,000, 145,000, 65,000, and 20,000-24,000 as determined by Western blots. Three of the antigens from neural tissue copurify and comigrate electrophoretically with neurofilament proteins. Polyclonal antibodies prepared against authentic neurofilament proteins react with antigens having molecular weights identical to those of proteins that react with immunoglobulins from the SCCL-VPNS patients. Polyclonal antibodies that were prepared against isolated retinal ganglion cells and that were shown previously to cause the immunoablation of the ganglion cells in vivo reacted most intensely with the Mr 205,000 antigen and weakly with the Mr 145,000 and Mr 70,000 antigens. Treatment of the Western blots with alkaline phosphatase from Escherichia coli did not affect the immunoreactivity between the immunoglobulins and the purified neurofilament proteins. It is proposed that the immunoglobulins in the sera of patients with SCCL-VPNS may be involved etiologically in the development of the VPNS.