Fig. 2

Biodistribution of ⁶⁴Cu-LLP2A. Ex vivo γ-counting (A) confirms increased lung uptake of ⁶⁴Cu-LLP2A at 2 and 4 weeks after bleomycin-induced fibrotic injury, which is blocked by co-injection of excess unlabeled LLP2A (ex vivo γ-counting was not performed at 1-week post-bleomycin as this timepoint was only assessed as part of the longitudinal PET/CT experiments). There are robust correlations between PET-derived (B ID/mL_mean and C %ID/mL_max) and γ-counting-derived measures of ⁶⁴Cu-LLP2A uptake, confirming the accuracy of noninvasive quantification of tracer uptake. γ-counting (D) and the visual assessment of whole-body PET (E) images demonstrate specific uptake of ⁶⁴Cu-LLP2A in organs rich in VLA-4-expressing cells, including spleen, thymus, and bone marrow. However, ⁶⁴Cu-LLP2A uptake in these organs is not significantly affected by bleomycin administration. N = 6 (control), 6 (2-week), 8 (4-week), and 4 (2-week blocked)