Decreased interferon synthesis and responsiveness to interferon by leukocytes from multiple sclerosis patients given natural alpha interferon.

Despite the use of interferon (IFN) in numerous clinical trials, relatively little is known about how IFN therapy influences leukocyte function. To evaluate some of its effects, leukocytes from multiple sclerosis (MS) patients given daily treatments of natural alpha IFN (IFN-alpha) were evaluated for IFN synthesis and two responses to IFN in vitro: enhancement (priming) of IFN synthesis and suppression of Concanavalin A (Con A)-induced T-cell mitogenesis. The IFN therapy had no effect on the sensitivity of Con A-stimulated leukocytes to the antiproliferative action of IFN-alpha. However, using Newcastle disease virus (NDV), measles virus, or poly I:C to stimulate IFN synthesis, cells from IFN-treated patients produced less IFN in response to all inducers, with titers ranging between 11% and 44% of pretherapy values. Also, unlike cells from these same patients before therapy or from the placebo recipients, cells from the IFN recipients were not primed by either IFN-alpha or -beta even though IFN-beta had not been used for therapy. The loss of these priming reactivities suggests that resistance to IFN had developed in IFN-treated patients.