Figure 4.
The top section shows blood sample collection from a patient's arm, the blood sample in a test tube, and the measurement of patient ADA2 activity using a machine. The bottom section illustrates the in vitro process where a plasmid with variant ADA2 is introduced into 293T cells. These cells are then cultured, and after 72 hours, the medium is collected and ADA2 activity is measured using a machine. The activity is reported as a percentage of wildtype activity.
Residual ADA2 activity of patients and variants are distinct properties. Above: Patient ADA2 activity is measured in blood samples ex vivo. Values were reported by the respective centers, commonly in mU/g. Below: The ADA2 activity of a specific genetic variant can be determined in vitro by expressing the variant in question in a cell line. ADA2 activity is then measured from the supernatant medium and reported as percentage of wild-type activity. Lee et al. established this for a number of common ADA2 variants, and classified the residual ADA2 activity as high (>3%), low (<3%), or zero (13). Our analysis is based on the published values.