The results did not qualitatively change when we restricted the analysis to the severe anti-ACE2 IgM–positive patients above and compared them to all severe COVID-19 patients from the CROWN Registry for whom anti-ACE2 IgM status was unknown (IgM-positive: mean = 37.53, S2 = 0.64, n = 721 on M = 18 unique patients; IgM-unknown: mean = 37.11, S2 = 0.59, n = 14827 on M = 473 unique patients; χ2 = 19.98, P = 0.0005 from linear mixed effects model Wald test with 4 degrees of freedom) (see Statistics and Supplemental Figure 3). Here, CD40LG is linked to COVID-19.