Immunological monitoring of azathioprine treatment in multiple sclerosis patients.

Despite the longstanding clinical use of azathioprine as an immunosuppressive agent in multiple sclerosis, little is known about the action of this drug on a number of parameters of putative pathogenic relevance in the disease. Eleven patients with multiple sclerosis, treated with azathioprine 2.5-3 mg/kg per day, and six untreated patients were studied with serial blood sampling for 1 year. The following immunological parameters were investigated: peripheral blood lymphocyte subsets, natural killer activity, serum IgG, IgM, ICAM-1 and tumour necrosis factor alpha (TNF-alpha). The most relevant changes included a decrease in CD3- CD56+ cells, an increase in CD4+ CD45RA+ cells and a decrease in TNF-alpha levels only in treated patients, while no changes occurred in untreated patients over a 1-year period. The decrease in TNF-alpha levels and the increase in "suppressor-inducer" lymphocytes could reduce chronic inflammation in multiple sclerosis, and paralleled an overall favourable clinical response to azathioprine treatment in our patients.