Objective: To investigate the effects of interferon beta treatment on T-cell interferon gamma binding (which is a possible marker for T-cell-dependent immune function) in patients with multiple sclerosis (MS).

Methods: Assay interferon gamma binding on T lymphocytes from patients with stable relapsing-remitting MS before, 3 months after, and 6 months after initiating interferon beta-1b treatment. Methods: The study was performed on ambulatory patients in a tertiary care center, where patients were diagnosed as having definite MS. Methods: Eighteen patients with clinically definite, stable, relapsing-remitting MS (13 women and 5 men; mean age [+/-SD] 32.6+/-7.1 years) were selected consecutively. Clinical status was defined according to the Kurtzke Expanded Disability Status Scale. All patients were treated with 8 x 10(6) IU interferon beta-1b subcutaneously every other day. Eighteen age- and sex-matched healthy subjects with no family history of neuropsychiatric disorders formed the control group.

Results: T lymphocytes from untreated patients with MS had significantly smaller amounts of interferon gamma receptors than those from control subjects (638+/-7 [SE] vs 707+/-11 [SE] receptors per cell). After 3 months of interferon beta-1b treatment, they showed a significant increase in interferon gamma binding (681+/-9 [SE] receptors per cell). After 6 months, T-cell interferon gamma maximal receptor values were even higher (700+/-7 [SE] receptors per cell), only slightly lower than those of control subjects.

Conclusions: Given that reduced interferon gamma binding might be related to lymphocyte activation, our data seem to demonstrate that the major effect of interferon beta-lb treatment is a decrease in T-cell activation.