Ex vivo functional characterization of circulating BLT1⁺ T cells. (A) Representative FACS plots of IFNγ and IL-4 production by different CD4⁺ T-cell subsets. Percentage of gated populations is shown in quadrants. (B) Circulating BLT1⁺ CD4⁺ memory T cells are more polarized than BLT1^– CD4⁺ memory T cells. Negatively selected magnetic bead–purified peripheral blood CD4⁺ T cells were prelabeled and then activated for 4 hours with PMA and ionomycin before fixation and permeabilization for cytokine analysis. BLT1⁺ CD45RA^– CD4⁺ T cells were 1.6 ± 0.2-fold more enriched for IFN-γ–producing Th1 cells (P = .036; n = 5), 2.3 ± 0.6-fold more enriched for IL-4–producing Th2 cells (P = .04; n = 5), and 4.1 ± 2.8-fold more enriched for both IFNγ- and IL-4–producing Th0 cells (P = .012; n = 5) compared with BLT1^– CD45RA^– CD4⁺ memory T cells. *P < .05 compared with total CD4⁺ T cells, and **P < .05 compared with BLT1^– CD45RA^– CD4⁺ T cells. Symbols represent individual study subjects. (C) Representative histogram plots of IFNγ production and perforin expression by BLT1⁺ and BLT1^– CD8⁺ T-cell subsets. (D) A large percentage of circulating BLT1⁺ CD8⁺ memory T cells rapidly produce IFNγ but lack significant perforin expression. As described above, purified peripheral blood CD8⁺ T cells were prelabeled and then activated for 4 hours before analysis for IFNγ production, or freshly isolated unactivated PBMCs were stained for intracellular perforin. After stimulation, total BLT1⁺ CD8⁺ T cells contained 2.9 ± 1.1-fold more IFNγ-producing cells than did BLT1^– CD8⁺ T cells (P = .007; n = 5), and BLT1⁺ CD45RA⁺ CD8⁺ T cells contained 5 ± 2-fold more IFNγ-producing cells than did BLT1^– CD45RA⁺ CD8⁺ T cells (P = .001; n = 5). *P < .05 compared with total CD8⁺, and **P < .05 compared with BLT1^– RA⁺ CD8⁺ memory T cells. Symbols represent individual study subjects. (E) Sorted FSC^hi CD4⁺ and CD8⁺ T-cell lymphocytes chemotax to LTB₄, but FSC^lo CD4⁺ and CD8⁺ T cells do not. These data are representative of 3 to 6 separate experiments. (F) CP-105696 (10 nm) inhibits LTB₄-mediated chemotaxis of FSC^hi CD4⁺ and CD8⁺ T cells. These data are representative of at least 3 separate experiments.