Ma1, a novel neuron- and testis-specific protein, is recognized by the serum of patients with paraneoplastic neurological disorders.

The identification of antineuronal antibodies has facilitated the diagnosis of paraneoplastic neurological disorders and the early detection of the associated tumours. It has also led to the cloning of possibly important neuron-specific proteins. In this study we wanted to identify novel antineuronal antibodies in the sera of patients with paraneoplastic neurological disorders and to clone the corresponding antigens. Serological studies of 1705 sera from patients with suspected paraneoplastic neurological disorders resulted in the identification of four patients with antibodies that reacted with 37 and 40 kDa neuronal proteins (anti-Ma antibodies). Three patients had brainstem and cerebellar dysfunction, and one had dysphagia and motor weakness. Autopsy of two patients showed loss of Purkinje cells, Bergmann gliosis and deep cerebellar white matter inflammatory infiltrates. Extensive neuronal degeneration, gliosis and infiltrates mainly composed of CD8+ T cells were also found in the brainstem of one patient. In normal human and rat tissues, the anti-Ma antibodies reacted exclusively with neurons and with testicular germ cells; the reaction was mainly with subnuclear elements (including the nucleoli) and to a lesser degree the cytoplasm. Anti-Ma antibodies also reacted with the cancers (breast, colon and parotid) available from three anti-Ma patients, but not with 66 other tumours of varying histological types. Preincubation of tissues with any of the anti-Ma sera abrogated the reactivity of the other anti-Ma immunoglobulins. Probing of a human complementary DNA library with anti-Ma serum resulted in the cloning of a gene that encodes a novel 37 kDa protein (Mal). Recombinant Mal was specifically recognized by the four anti-Ma sera but not by 337 control sera, including those from 52 normal individuals, 179 cancer patients without paraneoplastic neurological symptoms, 96 patients with paraneoplastic syndromes and 10 patients with non-cancer-related neurological disorders. The expression of Mal mRNA is highly restricted to the brain and testis. Subsequent analysis suggested that Mal is likely to be a phosphoprotein. Our study demonstrates that some patients with paraneoplastic neurological disorders develop antibodies against Mal, a new member of an expanding family of 'brain/testis' proteins.

Absence of antibodies to non-NMDA glutamate-receptor subunits in paraneoplastic cerebellar degeneration.

OBJECTIVE: To determine whether patients with antineuronal antibody-associated paraneoplastic cerebellar degeneration (PCD) harbor antibodies to non-N-methyl-D-aspartate glutamate receptors (GluRs) in their serum. BACKGROUND: A recent study identified antibodies to GluRs in the serum of patients with PCD. METHODS: Sera of 35 patients with PCD (20 anti-Yo, 5 anti-Ri, 5 anti-Tr, and 5 anti-Hu) were examined by immunohistochemistry and immunoblot techniques. The expression of GluRs was obtained after transfection of 293T cells with cDNA plasmids corresponding to GluR1, GluR2, GluR3, GluR4, GluR6, and GluR7. The tumors of four patients with anti-Yo-associated PCD and nine ovarian carcinomas from patients without PCD were examined for the expression of GluRs. RESULTS: The expression of each GluR subunit was confirmed using affinity-purified antibodies against the corresponding GluRs and with whole sera from two rabbits immunized with GluR3. Thirty-two sera from patients with PCD were negative and 3 showed equivocal reactivity with 293T cells expressing different GluRs. None of the 35 sera had a pattern of reactivity characteristic of any GluR antibody on immunohistochemistry of sections of rat brain. Eleven of 14 tumors did not express GluRs; only some cells of one paraneoplastic tumor expressed GluRs. CONCLUSIONS: That patients with antibody-associated PCD (anti-Yo, -Ri, -Tr, and -Hu) harbor GluR antibodies in their sera is unlikely. GluR antibodies cannot be used as markers of paraneoplastic neurologic disorders.