Search

HnRNP antigen from HeLa cells was purified using a monoclonal antibody (383 IgM) that recognizes heterogeneous nuclear ribonucleoprotein (hnRNP). From extracts of HeLa cells radiolabelled with 32P, this antibody immunoprecipitates relatively large RNAs of heterogeneous size which are synthesized in the presence of actinomycin D at doses which suppress synthesis of ribosomal RNAs (characteristic features of heterogeneous nuclear RNA). In immunoblots, 383 IgM binds to seven polypeptides: one of approximately 23,000 daltons, three between 30.000 and 43,000 daltons which correspond to the known hnRNP polypeptides called Al. A2 and CI, one of approximately 50,000 daltons, and a doublet of approximately 120,000 daltons. These proteins comigrate through sucrose density gradients suggesting that they are physically associated. Thus, 383 IgM appears to define an epitope that is shared among a number of the protein components of hnRNP. This antibody has been used to design a simple and fast protocol which allows the determination of autoantibodies from human sera by ELISA. [ABSTRACT FROM AUTHOR]

During routine immunofluorescence studies of the serum of a patient with Sjögren's syndrome and lymphoma we detected antibodies giving a cytoplasmic pattern which did not correspond to previously described patterns found for autoantibodies. Using different cells and tissues as substrates for indirect immunofluorescence, including rat liver, rat small bowel, rat testicle, human thyroid, guinea-pig plasma cells and cultured human fibroblasts, the cytoplasmic structure to which these autoantibodies are directed seems to he the golgi complex, a conclusion supported by histochemical studies. Furthermore, these antibodies were absorbed by isolated golgi vesicles. The autoantibodies are of IgG and IgA classes, and the antigen(s) with which they react is(are) resistant to treatment with DNAase and RNAase. None of the sera from 50 normal individuals, seven patients with Sjögren's syndrome (five of them primary and two associated with rheumatoid arthritis; none of them with lymphoma), 25 patients with mixed connective tissue disease, 10 patients with systemic lupus erythematosus and five patients with progressive systemic sclerosis, had antibodies directed against this cytoplasmic specificity, as determined by indirect immunofluorescence. This is the first time that autoantibodies directed to the golgi complex are reported. The significance of this finding awaits further descriptions in patients with a clinical picture similar to the one reported here. [ABSTRACT FROM AUTHOR]