Frequency of unconventional HLA-E_UL40 CD8 T-cell responses compared to conventional HLA-A*02_pp65 CD8 T-cell responses in HCMV⁺ kidney transplant recipients and healthy volunteers.

<p>PBMCs were isolated from freshly or prospectively harvested at M12 post-transplantation blood samples issued from healthy donors (HV) or from kidney transplant recipients (KTR), respectively. <i>Ex vivo</i> detection of HLA-E_UL40 CD8 T and HLA-A*02_pp65 CD8 T cells was performed using flow cytometry by selecting CD3⁺ CD8α⁺ TCRγδ^- tetramer⁺ cells on PBMCs. Detection threshold was 0.1% of total CD8 αβT cells and kidney transplant recipients and healthy volunteers bearing ≥0.1% of HLA-E_UL40 CD8 T cells (in blue) or ≥0.1% HLA-A*02_pp65 CD8 T cells (in red) were considered as positive. Detection of both types of CD8 T-cell responses are indicated in violet. Absence of detection is shown in light grey in HCMV^- recipients and dark grey for HCMV⁺ hosts. Data shown are the number of individuals that display anti-HCMV CD8 T-cell responses. Frequencies of the CD8 T-cell subsets were calculated among subgroups for all (total), non HLA-A*02 and HLA-A*02 individuals and expressed as percentages (%).