CD4 and ataxia telangiectasia: In our AT patients, low counts of lymphocytes, absolute T and B cell numbers, and total CD4+ and CD8+ T cell numbers were observed, with a mean value of 1,663 lymphocytes, 1,295 T cells, 135 B cells, 723 CD4+ cells, and 512 CD8+ cells per microliter (μL), respectively (Table 2 and Fig. S1A-E), which is consistent with previous studies [25, 39].