In vivo persistence of expanded clones specific for bacterial antigens within the human T cell receptor alpha / beta CD4 super(-)8 super(-) subset

We analyzed the T cell receptor (TCR) rearrangements of 100 TCR- alpha / beta CD4 super(-)CD8 super(-) (double negative [DN]) T cell clines from normal individuals. We found that in four out of six donors this subset contains expanded clones that often account for 0.5% and, in one individual, even 7% of all peripheral blood lymphocytes. By combining limiting dilution analysis and N region oligotyping of polymerase chain reaction amplified TCR cDNA, we could measure the clonal size and show that two of these expanded clones remain stable in size for up to 4 yr in peripheral blood. The results indicate that large clonal size and persistence are distinctive features of alpha / beta DN cells specific for bacterial antigens. These cells may use antigen-presenting cells, restriction molecules, and selection routes different from those used by antigen-specific CD4 super(+) T cells.