Donor Tcon proliferation is reduced in the presence of donor NK cells. (A) Average photons emitted from luc⁺ donor T cells in animals receiving TCD-BM, TCD-BM plus luc⁺ Tcons, or TCD-BM plus luc⁺ Tcons and donor NK cells; n = 4-5 animals per group, representative of 2 experiments. Signal intensity is higher in luc⁺ Tcon compared with luc⁺ Tcon + NK animal (P < .05, day 6). Error bars represent SE. (B) Donor Tcons reisolated from spleen and lymph nodes of mice that underwent transplantation are gated on the donor marker CD45.1, and CD4 and CD8. (C) CFSE histograms of donor Tcons reisolated from pLN on day 4 in the presence (Tcon + NK) or absence (Tcon) of donor NK cells. More CD4⁺ and CD8⁺ cells have divided in the Tcon group. Percentage of undivided cells is indicated. One representative FACS of 4 pooled mice is shown, representative of 2 independent experiments. (D) Mean fluorescence intensity of CFSE staining for CD4⁺ (top) and CD8⁺ (bottom) cells reisolated from pLN on day 4 in the presence (Tcon + NK) or absence (Tcon) of donor NK cells. A significantly lower mean fluorescence intensity (MFI) (*P < .001 for CD4⁺ and CD8⁺) was observed in Tcon groups.