Variable galactocerebroside expression by human Schwann cells in dissociated and peripheral nerve explant cultures.

It has been well established that rat Schwann cells down regulate their cell-surface expression of galactocerebroside (GalC) in vitro under normal cell culture conditions. To determine whether human Schwann cells exhibit a similar down-regulation of GalC in vitro we examined GalC expression in dissociated human Schwann cell cultures derived from normal adult peripheral nerve. Twenty-four hours post-dissociation up to 63% of human Schwann cells were found to express detectable levels of GalC on their surface whereas less than 8% of the Schwann cells expressed detectable levels of GalC at 14 days post-dissociation. In contrast, after nearly 3 months of peripheral nerve explant culture, greater than 30% of human Schwann cells still retained their GalC expression. A similar pattern was also observed when analyzing Schwann cell purity with dissociated cultures exhibiting a rapid decrease in Schwann cell purity under normal culturing conditions although Schwann cell purity was found to be largely unaffected during the period of peripheral nerve explant culture. In summary, we found there was less variation in both GalC expression and Schwann cell purity with time in peripheral nerve explant cultures than dissociated cultures.

High-titre IgM anti-sulfatide antibodies in individuals with IgM paraproteinaemia and associated peripheral neuropathy.

The common association between monoclonal gammopathy and peripheral neuropathy was studied in seven patients with demyelinating polyneuropathy and IgM paraproteinaemia. Plasma samples from these individuals were thoroughly tested for antiperipheral nerve myelin (PNM) antibodies and then screened for glycoprotein and glycolipid reactivity by western immunoblotting and thin-layer chromatography (TLC) immunostaining. Three of the seven samples showed strong IgM anti-PNM and antisulfatide (GalS) antibody reactivity. Two of these three plasma samples showed extraordinarily high antisulfatide IgM antibody titres, ranging from 1 x 104 to 1 x 106 arbitrary units/L. These same samples also showed intense myelin staining of sciatic nerve sections (paraffin and cryostat) and teased nerve fibres. No axonal immunoreactivity was observed. These results suggest that high titre IgM antisulfatide antibodies may play a pathogenetic role in the immune demyelination associated with IgM paraproteinaemia.

High titre anti-sulphatide antibodies in HIV-infected individuals.

Plasma samples from 35 individuals with human immunodeficiency virus (HIV) infection but without peripheral neuropathy were screened by enzyme linked immunosorbent assay (ELISA) for IgM and IgG antibodies against sulphatide (GalS). Five of these were shown to contain raised anti-GalS IgM antibody titres, while six had raised IgG titres. All plasma samples screened were compared to an internal neurological disease control which contained raised anti-GalS IgM antibody titres. Anti-GalS IgM antibody titres in the HIV cohort ranged between 200 and 2000 arbitrary units/litre (AU/l), whereas, IgG titres were between 200 and 10,000 AU/l. Two of four plasma samples from HIV-infected individuals with neuropathy (HIV+PN) also showed IgM reactivity with GalS; one also binding to the gangliosides GM1, GD1a, GD1b and GT1b. The other two samples showed IgG reactivity against GalS. These data indicate that antibodies against GalS occur more frequently in HIV infection than in HIV-seronegative individuals with and without neurological disease and may participate in the pathogenesis of neuropathies associated with HIV infection.

Peripheral nerve binding patterns of anti-sulphatide antibodies in HIV-infected individuals.

HIV-positive plasma samples from patients with and without neuropathy and with high titre anti-GalS antibodies showed strong binding to the myelin membrane of both fixed and unfixed human sciatic nerve specimens. This staining pattern was also seen with a plasma sample from a patient with IgM paraproteinaemic inflammatory demyelinating neuropathy with anti-GalS IgM antibody. Teased nerve fibres incubated with these anti-GalS antibodies from both HIV and non-HIV plasma samples showed immunofluorescence at the paranodal regions and Schmidt-Lanterman incisures. These data support a potential role for these antibodies in the aetiology of HIV-associated immune mediated neuropathies.

Antibodies against peripheral myelin glycolipids in people with HIV infection.

Plasma samples from 35 individuals with HIV infection but without clinical peripheral neuropathy were screened by ELISA for IgM and IgG antibodies against peripheral myelin. Eighteen of the 35 samples (51%) showed IgM reactivity and 11 (31%) showed IgG reactivity. By comparison, none of 48 samples from healthy blood donors showed IgM or IgG reactivity. Epitopes reacting with these antibodies were identified by TLC immunostaining as sulphatide (GalS) and the gangliosides GM1, GD1a and GD1b. Plasma samples from four people with HIV infection and neuropathy (HIV+PN), six HIV-seronegative individuals with IgM paraproteinaemic demyelinating neuropathy (IgMPDN) and 12 HIV-seronegative individuals with a variety of other neurological disorders (HIV-OND) were also investigated. Two of the four HIV+PN samples showed IgM reactivity with GalS; and two showed IgG reactivity against GalS. Of the six IgMPDN samples, three showed IgM reactivity with GalS. These data indicate that antibodies against peripheral myelin glycolipids, in particular GalS, occur more frequently in HIV infection than in HIV-seronegative individuals with and without neurological disease, and may contribute to subclinical neuropathy in HIV infection.