Defective CHS in BLT1/2^−/− mice. (A) WT and BLT1^−/− mice were sensitized on the shaved abdominal skin with 50 μL of 0.5% DNFB in 4:1 acetone/olive oil (vol/vol) and 5 μL on each footpad. Five days later, mice were challenged on the right ear (10 μL of 0.2% DNFB on each side). The left ear was painted with vehicle as control. Increases in ear swelling were measured at different time points. Mean values ± SE for each group (5 mice) are presented. (*P < .05, **P < .01 by t test, vs respective WT control group). One experiment representative of 3 is shown. (B) Histology, hematoxylin and eosin–stained tissue sections from WT and BLT1/2^−/− mice after 24 hours read-out CHS. The top row represents a ×100 magnification; an enlarged region of the same pictures is shown in the bottom row. Images were acquired using a Carl Zeiss Axioskope Optical Microscope equipped with an Achroplan 10 ×/0.25 NA objective and a 10 × eyepiece. Images were captured using a Nikon CoolPix 3.34 Megapixel camera (Nikon, Tokyo, Japan) at a fine resolution of 1600 × 1200 pixels in JPEG format and processed using Adobe Photoshop (Adobe Systems, San Jose, CA). (C) Defective capacity of BLT1/2^−/− DCs to elicit CHS. WT mice were immunized (on day −5) by subcutaneous injection of DNBS-loaded DCs (10⁶/mouse) obtained from WT or BLT1/2^−/− mice. Mice were challenged 5 days later (day 0) by ear painting with DNFB. Figure represents the values for ear swelling (mean ± SE) of 5 mice per group, and is representative of 3 experiments. **P < .01 by t test.