Immunoglobulin G subclass preference of intrathecally produced HIV-specific oligoclonal antibodies

Subclass of IgG antibody to GM1 epitope-bearing lipopolysaccharide of Campylobacter jejuni in patients with Guillain-Barré syndrome

Sera of patients who develop Guillain-Barré syndrome (GBS) subsequent to Campylobacter jejuni enteritis frequently have IgG anti-GM1 antibody. Lipopolysaccharide (LPS) of C. jejuni isolated from a GBS patient has a GM1 ganglioside-like structure. IgG subclass distribution of the anti-GM1 antibody in GBS patients is mainly restricted to IgG1 and IgG3. Since IgG antibodies to bacterial polysaccharide generally are restricted to IgG2 subclass, some investigators have assumed that either the general rules for immune response to LPS are broken in the patients or an alternative antigen has yet to be identified. To clarify whether the LPS participates in the production of the anti-GM1 antibody, we investigated the subclass of IgG antibody to the LPS that bears GM1-like structure. The subclasses of IgG antibody to the LPS were restricted predominantly to IgG1 and IgG3. The GM1 epitope-bearing LPS may function in the production of the anti-GM1 antibody in patients with GBS subsequent to C. jejuni infection.

Immunoglobulin-G isotype changes in human sporadic amyotrophic lateral sclerosis (ALS)

Out of 50 patients with sporadic amyotrophic lateral sclerosis (sALS), excluding 8 patients with recent immunosuppressive medication or low total IgG, we examined all available 92 sera of 11 women and 31 men nephelometrically for serum immunoglobulin concentrations including IgG isotypes IgG1-4. Mean serum levels of IgA and IgM remained within references in all cases. Isotypes IgG1 and IgG3 were the most frequently altered immunoglobulins. Without specific treatment, 34 out of 42 patients (= 80%) and 58 out of 92 sera (= 63%) demonstrated low IgG3 concentrations (< 0.41 g/l), while 14 patients (= 33%) and 20 sera (= 22%) demonstrated low IgG1 serum levels (< 4.22 g/l). In patients with normal total IgG, isotypes IgG1 and IgG2 often changed in a complementary way, and IgG1/IgG2 serum concentrations correlated significantly (rs = -0.518, P < 0.001). In four longitudinally monitored patients, the IgG3 isotype ranged from 1.3% to 8.2% of serum IgG and demonstrated a remarkable individual variability over time, corresponding to the relatively short half-life of IgG3. Since elevated circulating immune complexes may fluctuate rapidly, altered serum immunoglobulin isotypes could become more convenient parameters in a still enigmatic disease. To assess their role and relevance, their association with clinical course, cerebrospinal fluid and circulating immune complexes has to be examined.