Remarkably, r/r DLBCL patients had significant lymphopenia compared to healthy controls (HC) (1009 ± 927 x106/L versus 1785 ± 478 x106/L; P<0.001), due to reduced CD3+CD4+ T helper (297 ± 236 x106/L versus 735 ± 229 x106/L; P<0.001) and CD3-CD56+ NK cell numbers (164 ± 218 x106/L versus 313 ± 176 x106/L; P=0.009). Here, CD4 is linked to lymphopenia.