Decreased IL-10-producing regulatory B cells in patients with advanced mycosis fungoides.

Background: Historically, B cells have been considered as positive regulators of humoral immune responses. Specific B-cell subsets, however, negatively regulate immune responses and are termed "regulatory B cells" (Bregs). Recently, Bregs have been linked to not only inflammatory and autoimmune diseases, but also malignancies via suppressing anti-tumour immunity.
Objectives: To investigate the involvement of Bregs in advanced mycosis fungoides (MF).
Materials & Methods: The frequency of CD19 ⁺ CD24 ^hi CD27 ⁺ memory B cells and CD19 ⁺ CD24 ^hi CD38 ^hi transitional B cells (which enrich IL-10-producing Bregs) was examined in peripheral blood from patients with advanced MF (n = 11) and healthy controls (n = 9) by flow cytometry. The frequency of IL-10-producing Bregs was also measured by flow cytometry. The correlation between frequency or number of B-cell subsets and disease severity markers was also analysed.
Results: The frequency of CD19 ⁺ CD24 ^hi CD27 ⁺ B cells, CD19 ⁺ CD24 ^hi CD38 ^hi B cells, and IL-10-producing B cells was decreased in peripheral blood of advanced MF patients. The frequency and number of these B-cell subsets inversely correlated with serum soluble IL-2 receptor and serum lactate dehydrogenase levels.
Conclusions: The development of IL-10-producing Bregs is impaired in patients with advanced MF and a decrease in IL-10-producing Bregs may play an important role in the progression of advanced MF.