IL6 and COVID-19: In addition, the association between these parameters and kynurenine and its metabolites (e.g., quinolinic acid, a neurotoxicant) is consistent with the recently reported linkage of dysregulated kynurenine metabolism in RBCs at the time of donation with increased osmotic fragility and lower post-transfusion hemoglobin increments (33) or elevated proinflammatory cytokines like IL-6 and IFN-γ in the context of COVID-19 (58) or after strenuous exercise (59).