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

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 κ and λ chains. Hybridization with the six Vκ and the 4 Vκ human family probes was observed in serial sections, providing additional evidence that individual germinal centres were polyclonal. The thymic B ceil repertoire closely reflected the VH and the Vκ family usage of normal peripheral blood lymphocytes with the preferential utilization of VH3, Vκl and Vκ3. [ABSTRACT FROM AUTHOR]