Figure 6.

ICAM-1 and TfR identify polarized states of macrophage subpopulations during ALI. To identify changes in expression for ICAM-1 and TfR, we calculated the mean fluorescence intensity (MFI) for TfR, ICAM-1, and their respective isotype control samples. ΔMFI was calculated for each sample, and results are expressed as mean ΔMFI ± SEM for Group I (top row, A–D), Group II (middle row, E–H), and Group III (bottom row, I–L). Group I macrophages in both compartments (solid bar, interstitial; gray bar, alveolar) showed the greatest increase in ICAM-1 expression during the induction phase of ALI, identifying M1 polarization in these resident cells. However, ICAM-1 was also highly expressed in recruited cells (Group III) during the resolution phase. TfR expression was significantly increased during the resolution phase in Groups I and III, peaking on Day 4, and on Day 1 in Group II. *P < 0.05, with Day 0 or Day 1 as reference group, as already noted (n = 6–9 samples per time point). The significance of the raw MFI for TfR and ICAM-1 compared with their respective isotype control samples was determined using the Student t test. Except where indicated as nonsignificant (NS), all findings were significant at P < 0.05.