Opposite effects of interferon-β on new B and T cell release from production sites in multiple sclerosis patients

The release of newly produced B and T lymphocytes from the production sites was analyzed in 30 multiple sclerosis patients treated with interferon-beta by measuring T-cell receptor excision circles and k-deleting recombination excision circles. We found that the therapy induces opposite effects on B- and T-cell mobilization in 33% of patients. New B-cell production, which peaks after 6 months of therapy and then decreases to levels that, however, are still higher than in controls, may cause a renewal of the B-cell compartment. On the contrary, the decreased number of newly produced T lymphocytes observed at 12 months of treatment and the association between reduced thymic output and low peripheral T lymphocytes can be a cause of leukopenia, a frequent side effect of the therapy.