Production of viral antibodies in vitro by CSF cells from mumps meningitis and multiple sclerosis patients

MS and clinically isolated syndromes: shared specificity but diverging clonal patterns of virus-specific IgG antibodies produced in vivo and by CSF B cells in vitro

BACKGROUND

Intrathecal synthesis of oligoclonal IgG antibodies against measles virus (MeV), varicella zoster virus (VZV) and herpes simplex virus type-1 (HSV-1) is a characteristic feature multiple sclerosis (MS).

METHODS

We have used isoelectric focusing-immunoblot to define the clonal patterns of IgG and of IgG antibodies to MeV, VZV and HSV-1 in supernatants of in vitro cultures of peripheral blood lymphocytes (PBL) and cerebrospinal fluid (CSF) cells and in sera and CSF from three patients with MS and three patients with clinically isolated syndromes (CIS) suspective of demyelinating disease.

RESULTS

In vitro synthesis of IgG by PBL was not detected in any patient. In contrast, in vitro synthesis by CSF cells of oligoclonal IgG and oligoclonal IgG antibodies to one or two of the three viruses tested was observed in all six patients. The clonal patterns of the in vitro synthesized IgG and virus specific IgG differed to varying extent from those synthesized intrathecally in vivo. However, in each patient, the in vitro and in vivo intrathecally produced antibodies displayed specificity for the same viruses. The addition of B cell activating factor (BAFF) had no effect on the amounts or clonal patterns of either total IgG or virus-specific IgG produced by CSF cells in vitro.

CONCLUSION

Virus specific B cells capable of spontaneous IgG synthesis are clonally expanded in the CSF of patients with MS. The B-cell repertoire in CSF samples is only partially representative of the intrathecal B-cell repertoire.

Affinity of antigen-specific IgG distinguishes multiple sclerosis from encephalitis

The characteristics of antigen-specific IgG in patients with multiple sclerosis and patients with encephalitis have been compared. Both groups of patients showed antigen-specific oligoclonal bands locally synthesised in the CSF. When the affinity distribution of the antigen-specific IgG was measured there was a marked difference between the two groups. Encephalitis patients had high affinity antibody against the causative antigen. This was consistent with the antibody undergoing affinity maturation as a result of the immune system fighting a primary infection. Multiple sclerosis patients lacked high affinity response. This lack of high affinity antibody was also seen in those encephalitis patients when antigens other than the causative antigen were studied.

B cells capable of spontaneous IgG secretion in cerebrospinal fluid from patients with multiple sclerosis: dependency on local IL-6 production

Cerebrospinal fluid (CSF) from multiple sclerosis (MS) patients contains B cells capable of spontaneous IgG secretion in vitro. This study analyses the function and regulation of these cells. CSF cells obtained from nine MS patients actively produced IgG during 2-3 days in culture, and the activity decreased when CSF cells were cultured in serum-free medium. CSF cells from four controls did not secrete detectable IgG in vitro. Further experiments revealed that IL-6 played a role on MS CSF IgG-secreting cells, as can be deduced from the following findings: (i) the addition of exogenous IL-6, but not of other cytokines, to serum-free cultures restored missing CSF cell IgG secretion (ii) the inclusion of anti-IL-6, but not of control, blocking MoAb reduced IgG secretion by CSF cells in fetal calf serum (FCS)-containing cultures; and (iii) CSF cells were capable of active IL-6 production in the presence of FCS. These results suggest that endogenous IL-6 production by MS CSF cells seems to be responsible for inducing CSF IgG-secreting B cells to reach terminal differentiation.