Ex vivo phenotype and frequency of influenza virus-specific CD4 memory T cells.
Lucas M., Day CL., Wyer JR., Cunliffe SL., Loughry A., McMichael AJ., Klenerman P.
Recent advances in class II tetramer staining technology have allowed reliable direct ex vivo visualization of antigen-specific CD4 T cells. In order to define the frequency and phenotype of a prototype response to a nonpersistent pathogen, we have used such techniques to analyze influenza virus-specific memory CD4 T cells directly from blood. These responses are stably detectable ex vivo at low frequencies (range, 0.00012 to 0.0061% of CD4 T cells) and display a distinct "central memory" CD62L(+) phenotype.