The results showed no interaction between Lag3 and heparin‐induced Tau (hep‐Tau) PFF.[6] A recent study showed that hep‐Tau PFF is not an active seed in vivo, as compared to self‐seeded tau or the AD brain extracts‐induced Tau (AD‐Tau) PFF.[2d] Thus, we wondered whether bioactive tau, but not hep‐tau, fibrils bind to Lag3. Here, LAG3 is linked to Alzheimer disease.