Imbalance between T follicular helper and T follicular regulatory cells in myasthenia gravis

According to the signals they receive from the local environment, T cells can differentiate into one out of several subtypes, including Th1, Th2, Th3, Th9, Th17, T follicular helper (Tfh) and Treg cells (1). Each of these cell subsets possesses a particular function. The term “Tfh cell” first described a subset of CD4+ T cells present in human lymphoid tissues, namely tonsils, and functions primarily to provide help to B cells (2). Interestingly and similarly to B cells, Tfh cells express the homing receptor, CXCR5, whose ligand is the CXCL13, the main B cell chemoattractant chemokine. Within germinal centers (GC), Tfh cells mediate the selection and survival of B cells that differentiate into plasma cells producing high-affinity antibodies against foreign antigens, and memory B cells (3). Recently, a small subset of T follicular regulatory (Tfr) cells was described, that are Treg cells able to suppress specifically the Tfh cell function (4). Thus it is likely that a balance between Tfr and Tfh cells dictates the fate of the B cell immune response.