anti-Hu IgG Research Articles

Paraneoplastic anti-Hu serum: studies on human tumor cell lines

Patients with low titers of anti-Hu, the paraneoplastic encephalomyelitis/sensory neuronopathy (PEM/PSN) antibody, have a better tumor prognosis that those who do not harbor these antibodies. Accordingly, we examined the effects of serum from patients with anti-Hu antibodies on human tumor cell lines, in order to determine: (1) if the serum was toxic (growth inhibition or cytolysis) to tumor cells with or without complement, and (2) if anti-Hu antibodies contributed to tumor toxicity. The serum of 14 patients with anti-Hu associated PEM/PSN, 22 patients with small-cell lung cancer (SCLC) without anti-Hu antibodies, and 20 normal individuals were studied. Three cell lines (NT-2, BE(2)-C, and SH.SY5Y) that express Hu proteins, and one cell line (SAOS-2) that does not, were studied. We examined the effects of whole serum, IgG-depleted serum, and purified IgG in the presence or absence of complement. A higher percentage of anti-Hu sera were toxic (71%) compared with sera from anti-Hu negative SCLC patients (23%) ( p<0.0001). No correlation existed between the titer of anti-Hu antibodies and toxicity. The toxic effects were observed in all tumor cell lines including the cell line that does not express Hu antigens. Toxicity persisted in serum depleted of IgG. Purified anti-Hu IgG in the presence and absence of complement, was not toxic. Our findings indicate that anti-Hu serum is toxic for human tumor cell lines, but this toxicity does not appear to be mediated by anti-Hu antibodies.

Internalization of anti-Hu IgG is not Fc gamma receptor mediated.

Patients with paraneoplastic subacute sensory neuronopathy or encephalomyelitis associated with small cell lung cancer cells (SCLC) frequently harbor anti-Hu antibodies (also called antineuronal nuclear antibodies type 1) in serum and CSF. [1] These antibodies react with a family of nuclear proteins, with apparent molecular mass ranging from 35 to 45 kD, expressed in neurons and SCLC cells. [2] Anti-Hu antibodies are one example of ANA associated with autoimmune disease. ANA occur in a variety of autoimmune disorders, most classically systemic lupus erythematosus. The ability of these antibodies to interact with nuclear antigens in living cells has been questioned and the relevance of the antibodies to disease production doubted. However, several groups have demonstrated that autoantibodies can penetrate living cells. [3] Anti-Hu IgG penetrates viable Hu-positive SCLC cells and localizes in the nucleus. [4] How this IgG internalizes into the cell and translocates to the nucleus is unknown. Immunocytochemistry, immunoprecipitation, and flow cytometry show no Hu antigen on the cell surface (Lieberman and Hormigo, unpublished data; Posner, personal communication). Alternatively, internalization may be mediated by receptors that recognize the Fc portion of immunoglobulin molecules, the Fc gamma receptors (Fc gamma Rs). Fc gamma Rs comprise a family of molecules within the immunoglobulin superfamily. There are three main classes: Fc gamma RI, Fc gamma RII, and Fc gamma RIII. [5] For example, the internalization of …

Immunization with the paraneoplastic encephalomyelitis antigen HuD does not cause neurologic disease in mice.

Paraneoplastic encephalomyelitis/paraneoplastic sensory neuronopathy (PEM/PSN) associated with small cell lung cancer is characterized by high serum and CSF titers of anti-neuronal (anti-Hu) antibodies and by intrathecal synthesis of anti-Hu IgG. A pathologic role for the anti-Hu antibodies in PEM/PSN is further suggested by reported intraneuronal accumulation of the antibodies in the nervous system of PEM/PSN patients at autopsy. We immunized SJL/J mice, Lewis rats, and Hartley guinea pigs with purified recombinant HuD fusion protein. In spite of high-titer anti-HuD antibodies, neurologic and pathologic examination of the animals was normal. Apparent uptake of purified IgG by neurons in the brain proved to be artifactual.

Nuclear localization of anti-Hu antibody is not associated with in vitro cytotoxicity

IgG fractions of sera containing anti-Hu antibodies or control sera were influenced with Hu-positive and Hu-negative cell lines. Anti-Hu IgG specifically localized in the nucleus of Hu-positive cells. Anti-Hu-positive and control sera were incubated with Hu-positive cells and human complement or peripheral blood mononuclear cells. Hu antibody caused neither complement-mediated lysis nor augmented antibody-dependent cell-mediated cytotoxicity. Anti-Hu IgG did not affect proliferation of Hu-positive cells. Anti-Hu antibodies may not play a direct role in tissue injury in patients with paraneoplastic encephalomyeloneuropathy and anti-Hu antibodies.

Analysis of the IgG subclass distribution and inflammatory infiltrates in patients with anti-Hu-associated paraneoplastic encephalomyelitis.

Using immunohistochemistry, we studied the IgG subclass distribution of the anti-Hu antibody in serum, nervous system, and tumor of patients with anti-Hu-associated paraneoplastic encephalomyelitis/sensory neuropathy (PEM/PSN). The nervous system was also examined for deposits of complement and the distribution and type of inflammatory cells. IgG1 and IgG3 were the predominant isotypes of the anti-Hu IgG in serum, nervous system, and tumor. A few patients also had anti-Hu IgG2, but this isotype was not consistently present in all the regions of the nervous system studied. There was no correlation between neurologic symptoms and specific anti-Hu isotype, nor was there evidence that different anti-Hu isotypes recognized specific brain regions. Although IgG1 and IgG3 can activate complement, only weak complement reactivity was found, and that only in a few areas of the nervous system. This finding, in addition to the absence of natural killer (NK) cells, suggested that complement-mediated toxicity and antibody-dependent cell cytotoxicity mediated by NK cells are not pathogenic in PEM/PSN. Inflammatory infiltrates included CD19+ (B cells) and CD4+ (helper/inducer) cells in the perivascular spaces, and lymphocytes bearing CD8+CD11b- markers (cytotoxic T cells) in the interstitial spaces. Infiltrates of EBM11+ (monocyte/macrophage) cells were identified in the perivascular spaces (macrophage phenotype) and in those interstitial regions (microglial phenotype) with severe pathologic changes. The ability of the IgG1 and IgG3 isotypes to bind Fc receptors may have played a role in the recruitment of these monocyte/macrophage cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Paraneoplasia and Autoimmunologic Injury of the Nervous System: The Anti‐Hu Syndrome

In recent years, antineuronal autoantibodies of varying antigenic specificity have come to be associated with a number of paraneoplastic neurologic disorders. Anti-Hu is a polyclonal complement-fixing IgG directed against a 35 to 40 kilodalton protein concentrated in the nuclei of neurons throughout the central and peripheral neuraxes. Its elaboration at high titer in serum and cerebrospinal fluid is invariably associated with a neurologic syndrome characterized chiefly by subacutely evolving sensory neuropathy and an array of central disturbances that include bulbar and cerebellar dysfunction, limbic encephalitis and motor neuron disease. The manufacture of anti-Hu IgG is triggered in a great majority of cases by underlying small cell carcinomas of pulmonary origin, typically limited in stage and otherwise silent, that aberrantly express the native neuronal antigen or an antigenically indistinguishable epitope. Both neoplastic and diseased neural tissues contain lymphocytes of B and T lineage specifically cognizant of the Hu antigen as well as concentrated anti-Hu IgG bound to tumor cells and neurons, respectively. These observations suggest that an immune response serving initially to limit the growth and spread of its inciting neoplasm comes subsequently to be misdirected against the nervous system of the host, resulting in autoimmunologically-mediated neurologic injury. Clinical, neuropathologic and immunologic data derived from a series of 71 sero-confirmed cases of the anti-Hu-associated paraneoplastic sensory neuronopathy/encephalomyelitis complex are reviewed.

Detection of the anti‐Hu antibody in specific regions of the nervous system and tumor from patients with paraneoplastic encephalomyelitis/sensory neuronopathy

We studied the nervous systems and tumors of five patients with anti-Hu-positive paraneoplastic encephalomyelitis/sensory neuronopathy (PEM/PSN) to determine if the autoantibody found in the serum and CSF was also present in those tissues. Immunohistochemical studies of the nervous system revealed the presence of IgG bound predominantly to the nuclei of most of the neurons and the cytoplasm of some glial cells. IgG was also present to a lesser degree in the neuropil. In brains of patients who died of cancer without the paraneoplastic syndrome, IgG was present in the immediate perivascular areas and to a very limited degree in the neuropil. There was no IgG in neurons, and in only some of the controls a few glial cells showed IgG immunoreactivity in the cytoplasm. The amount of anti-Hu IgG relative to total IgG in various brain regions and tumor was determined by quantitative Western blot analysis. The proportion of anti-Hu IgG was greater in some areas of the brain and tumor than in serum and CSF. Control brains did not contain anti-Hu IgG. There was a limited correlation among (1) the principal clinical symptoms, (2) regions of major tissue injury, and (3) the quantitative anti-Hu IgG distribution. We conclude that although the role of the antibody in the pathogenesis of the disease is still uncertain, its specific localization in the nervous system and tumor suggests an immunologic etiology of this paraneoplastic syndrome.