Individual germinal centres of myasthenia gravis human thymuses contain polyclonal activated B cells that express all the Vh and Vk families.

SUMMARY Using in situ hybridization, we analysed the immunoglobulin repertoire expressed by the B cells present in myasthenia gravis thymuses from four patients. B cells, mostly in activated state, were clustered in germinal centres, in which multiple isotypes were identified. A majority of cells expressed IgG as compared with IgM. with a roughly similar contribution of k and δ chains. Hybridization with the six VH and the 4 Vk human family probes was observed in serial sections, providing additional evidence that individual germinal centres were polyclonal. The thymic B cell repertoire closely reflected the VH and the Vk family usage of normal peripheral blood lymphocytes with the preferential utilization of VH3, Vk1 and Vk3.