Deciphering the CD4+ T cell compartment in follicular lymphoma
Follicular lymphoma (FL) is the most frequent indolent lymphoma and results from the malignant transformation of germinal centre B cells in secondary lymphoid organs. Beside the genetic alterations associated with the deregulation of the anti-apoptotic protein Bcl2, the growth of malignant FL B cells relies on the development of a supportive microenvironment, which forms a specialized cell niche contributing to disease development, progression, and drug resistance. Several studies showed that malignant FL B cells are found admixed to specific immune cell subsets, in particular CD4+ T cells. In addition, the nature and the localization of T cells were associated with prognosis. This suggests that different functional CD4+ T cell subsets could play an important role in FL pathogenesis. Based on this hypothesis, we decided to explore the CD4+ T cell compartment found in close contact with FL B cells in malignant lymph nodes and demonstrated a high frequency of follicular regulatory and follicular helper T cells with specific features. These CD4+ T cell subsets emerge as a central therapeutic target, and evaluation of the proportion of these cells would be useful to better predict the biological effect of new drugs.