CXCR4 antagonism corrected peripheral blood CD4+ and CD8+ T-cell lymphopenia in these mice and even restored the circulating CD4/CD8 T-cell ratios to WT levels after 7 days (Supplementary Figures S3A–C; Table 1) and 28 days of treatment (Figures 3A–C). Here, CD4 is linked to lymphopenia.