Time-course of interleukin-2 receptor expression in interferon beta- treated multiple sclerosis patients

The time-course of CD25 (the 55-kD/α subunit of the interleukin-2 (IL- 2) receptor) expression on CD4 + T lymphocytes, and serum levels of soluble IL-2 receptors (sIL-2R) and IL-2 were evaluated in relapsing-remitting multiple sclerosis (RRMS) patients treated with interferon beta-1b (IFNβ1b). Peripheral blood samples were collected before therapy (TO), and 1 (T1), 2 (T2), 3 (T3), 6 (T4), and 12 (T5) months after therapy initiation. While at T1 and T2, half the patients showed an increased number of circulating CD4 + CD25 + lymphocytes and an up-regulation of CD25 expression, at T3 this T- cell subset was significantly reduced in all the patients. From T4 to T5, however, the progressive return to pretreatment values was observed. Serum sIL-2R levels were not significantly affected by IFNβ1b at any time point. IL-2 was detected in only a few patients at T0, and never at T1 to T5. The transient up-regulation of CD25 + expression that occurred in about 50% of the patients may explain the unchanged relapse rate observed during the first 2 to 3 months after starting IFNβ1b therapy. Our study demonstrates that IFNβ1b down-regulates CD25 expression in vivo. This effect, however, was observed only after 3 months of therapy, and was followed by the return to pretreatment values after 6 to 12 months. Taken all together, our findings suggest that IFNβ1b only transiently affects CD25 expression in vivo, and that this effect cannot account for the reported long-lasting beneficial action of IFNβ1b on RRMS.