ARG1 and Hodgkins lymphoma: When we measured circulating Arg-1 in the serum of an enlarged cohort of patients (training+validation sets), we found it was increased in HL patients at diagnosis compared to healthy volunteers, mean ± standard deviation (SD) 174.6 ± 10.3 versus 51.5 ± 4.9 ng/mL (N = 118, p < 0.0001, Figure 4A).