Human tonsillar germinal center T cells are a diverse and widely disseminated population

Germinal center (GC) T cells are a poorly investigated population with a unique helper-inducer memory phenotype. Murine GC T cells have been demonstrated to be oligoclonal and antigen specific. The aim of this study was to investigate the diversity of human tonsillar GC T cells. Immunohistochemistry with a panel of different TCRVbeta family antibodies and sequencing of TCRgamma gene rearrangements obtained from individual microdissected GC demonstrated local diversity of human tonsillar GC T cells. No evidence of local clonal dominance or of a local migratory pathway from the T cell zone to adjacent GC was seen. Primers specific to the junctional region of the TCRgamma gene of individual GC T cell clones were designed, and used to trace the dissemination of the clones. One was found to be concentrated locally. Both clones studied were present in both of the patient's tonsils, suggesting widespread dissemination. In addition, no evidence of somatic hypermutation was found in the TCRgamma gene sequences, or in expressed TCRalpha and beta gene sequences obtained by reverse transcriptase-PCR from isolated tonsillar GC.