CD27 and influenza: In our study, immunization by a virosome-formulated influenza vaccine primed peripheral blood T and B cell subsets for early recall responses to H1N1pdm, H1N2 and H3N2 strains, including central memory CD4+ T cells (CD4+CD27+CD45RA−), cytotoxic T lymphocytes (CD3e+CD8+), and B lymphocytes (CD79a+, CD79a+SWC7+CD5+ and CD79a+SWC7+CD5−).