Interferon-beta-1b increases serum interleukin-12 p40 levels in primary progressive multiple sclerosis patients.

Serum levels of interleukin-12 heterodimer (IL-12p70) and its homodimeric subunit (IL-12p40) were analyzed by enzyme-linked immunosorbent assay in 18 patients with primary progressive multiple sclerosis (MS) during 3 months before and 3 months under treatment with interferon-beta-1b (IFNbeta-1b, Betaferon(), eight million units (MIU) every other day subcutaneously). Median IL-12p40 levels in MS patients before treatment (66.5 and 63.9 pg/ml) were not elevated compared to 18 healthy controls. IL-12p40 significantly increased during treatment (P<0.0001, median 105.3 pg/ml after 1 month and 95.3 pg/ml after 3 months). Detectable serum levels of IL-12p70 before therapy were only found in one patient. IL-12p70 did not increase during treatment. These data show that immunological processes may also play a role in primary progressive MS and that IFNbeta-1b has an immunomodulating effect in this particular MS subtype.