CD40LG and COVID-19: When immune parameters were stratified by initial disease severity (Table 4), patients recovering from critical COVID-19 maintained significantly higher IgM levels compared to those with severe disease across all timepoints: month 3 (1.01 vs. 0.75 g/L, p = 0.033), month 6 (0.96 vs. 0.60 g/L, p = 0.040), and month 12 (0.92 vs. 0.45 g/L, p = 0.044).