Activated T helper cells, as well as other associated regulatory T or B cells, normally release cytokines (e.g., IL-10, IL-21) into the immunological synapse toward the antigen-presenting GC B cells, which may result in dysregulation within the DLBCL microenvironment in parallel to alterations in tumour-infiltrating T cell populations. Here, IL21 is linked to diffuse large B-cell lymphoma.