BACKGROUND:Lenalidomide, an immunomodulatory agent, has activity in lymphoproliferative disorders. The authors, therefore, evaluated its effects on T-cell immunophenotype and cytokine production in patients with chronic lymphocytic leukemia (CLL).METHODS:To study the immunomodulatory effects of lenalidomide in CLL, the authors recruited 24 patients with untreated CLL enrolled in a phase 2 clinical trial of lenalidomide and obtained peripheral blood specimens for immunologic studies consisting of enumeration of T cells and assessing their ability to synthesize cytokines after activation through T-cell receptor (TCR).RESULTS:After 3 cycles of therapy, patients had a significant reduction in percentage (%) and absolute lymphocyte count (ALC) and an increase in percentage of T cells, percentage of activated CD8+ T cells producing IFN-, and percentage of regulatory T (TR) cells when compared with their respective levels before treatment. After 15 cycles of treatment, responder patients had significant reduction in percentage of lymphocytes and ALC, percentage of activated CD4+ T cells producing IL-2, IFN-, or TNF-, and percentage of TR cells when compared with their perspective levels after 3 cycles of treatment. Furthermore, the numbers of activated CD4+ T cells producing IL-2, IFN-, or TNF-, activated CD8+ T cells producing IFN-, and TR cells normalized to the range of healthy subjects.CONCLUSIONS:Treatment with lenalidomide resulted in the normalization of functional T-cell subsets in responders, suggesting that lenalidomide may modulate cell-mediated immunity in patients with CLL. Cancer 2011;. © 2011 American Cancer Society.