Evaluation of CD4⁺ cells in tissues for 4Gyx2 TBI-transplanted monkeys. Baseline (A) and 2 hours postmobilization with AMD3100 (B) SPECT maximum intensity projection image of ZH32 with arrows pointing to specific tissues along with imaging standard. Baseline and longitudinal SPECT maximum intensity projection images (C) for up to 1 year following TBI of ZG21, ZH32, and ZG41 rhesus macaques. All images are adjusted within and among monkeys on the maximum liver uptake. Different image contrasts were applied to head and abdominal field of views to highlight clusters of LNs and spleen. Grayscale images were converted to rainbow colors with appropriate retention scales, where red color indicates high retention.