SPECT maximum intensity projection images. SPECT maximum intensity projection images comparing (C) 3Gyx2 (ZI12), (B) 4Gyx2 (ZG21, ZH32, ZG41), and (A) 5Gyx2 (ZG70, ZI64, and ZJ37) at day 6 post-TBI and (D) a chronically infected SHIVDH12R/SIVmac239 rhesus macaque (G43). Despite low circulating levels of CD4⁺ cells in all animals, residual CD4⁺ cells remain within LT such as the spleen following TBI, but more profound depletion is associated with chronic SHIV infection. 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.