T reg cell contacts with DCs suppress contemporaneous engagement by antigen-specific T conv cells in vivo. (A) The protocol for visualizing interactions between OT-II T cells and OVA323-339-presenting DCs that were exposed to T reg cells in the same LN. (B–G) Interactions between OT-II T cells and OVA323-339-presenting DCs that were exposed to transferred T reg cells in the LN. (B–D) Typical behaviors of OT-II T cells interacting with DCs visibly contacted (+; B) or untouched (–; C) by the transferred T reg cells. Arrowheads in B trace one T reg cell and two OT-II T cells (number 1 and 2) making contacts with the same DC. Arrowheads in C trace one OT-II T cell interacting with a DC free from transferred T reg cells. Closed arrowheads mark the beginning and end of an interaction incidence (see Videos 6 and 7). (D) Duration of contacts between OT-II T cells and DCs with (n = 25) or without (n = 23) T reg cell contacts. (E) Contact durations with T reg cell and OT-II cells by the same individual DCs analyzed in Fig. 3 (B–D). Each symbol represents one DC, and the trend line denotes the negative correlation. (F) Typical behaviors of OT-II T cells interacting with DCs visibly contacted by transferred T conv cells. Arrowheads in F trace three T conv cells (number 1, 2, and 3) and one OT-II T cell making contacts with the DC. (G) Duration of contacts between OT-II T cells and DCs with (n = 22) or without (n = 30) T conv cell contacts (see Video 9). Data are pooled from six imaging sessions. **, P < 0.01; N.S., not significant, Student’s t test.
