H4C15 encodes a histone H4 variant belonging to the clustered histone family. Based on limited published evidence, H4C15 was identified as a potential therapeutic target in severe community-acquired pneumonia (SCAP), where it showed differential expression in peripheral blood leukocytes and correlates with the NETosis pathway, a key mechanism implicated in SCAP pathogenesis 1. The specific molecular functions of H4C15 remain largely uncharacterized in the literature.