Presence of F-reactive DP8α T lymphocytes in the blood of healthy individuals.

<p>(a) Flow cytometry analysis of the frequencies of DP8α T lymphocytes in the blood of 18 donors: representative dot plot of PBMC co-labelled with anti-CD3, anti-CD4, and anti-CD8α antibodies, representative histogram of CD8β expression by gated CD8, CD4, and DP8α PBMC, and the percentages of DP8α lymphocytes among the CD3 and the CD3CD4 PBMC. (b) Proliferative responses of DP8α peripheral blood T cells to F in the presence or absence of an anti-MHC class-II antibody or an irrelevant antibody, and to B, L, and E. PBMC were cultured for 5 d with the antibody and/or indicated bacteria at a bacterium∶PBMC ratio 1∶1: representative FlowJo analysis of the VPD dilution and percentage of F-specific divided DP8α T cells in the PBMC from several donors (<i>n</i> = 18); ***<i>p</i><0.001 and **<i>p</i><0.01 (paired <i>t</i>-test). (c) Percent VPD dilution in paired DP8α and CD4 T cells among PBMC co-cultured with F for 5 d; ***<i>p</i><0.001 (paired <i>t</i>-test). (d) CTLA4 and LAG3 expression in proliferative DP8α and CD4 PBL after 5 d of co-culture with allogeneic monocytes loaded overnight with F (<i>n</i> = 2). (e) Flow cytometry analysis of the proliferative response of freshly isolated DP8α or CD4 PBL after 5 d of co-culture with autologous monocytes alone or loaded overnight with F or E: representative cytometry data of a freshly sorted DP8α PBL population and mean percentage of F-specific divided cells (calculated on FlowJo software) (experiments performed with five freshly isolated DP8α PBL (black circles) and two CD4 PBL (white circles).