A recombinant fusion protein composed of the extracellular domain of the mature human glycoprotein CD24 linked to a human immunoglobulin G1 (IgG1) Fc domain, with potential immune checkpoint inhibitory, anti-inflammatory and antineoplastic activities. Upon administration, the CD24 extracellular domain-IgG1 Fc domain recombinant fusion protein CD24Fc binds to injured cell components, also called DAMPs (Danger-Associated Molecular Patterns), thereby preventing the interaction of DAMPs with toll-like receptors (TLRs) and inhibiting both nuclear factor-kappa B (NFkB) activation and secretion of inflammatory cytokines. In addition, CD24Fc binds to and activates Siglec G/10, a sialic acid-binding immunoglobulin-type lectin, and stimulates SHP-1-mediated inhibitory signaling, preventing NFkB activation and secretion of inflammatory mediators, which further prevents inflammatory responses. DAMPs activate the innate immune system. CD24 binds to both DAMPs and Siglec G/10 to regulate immune responses.CD24/Siglec G/10 interaction plays a key role in a number of immune-mediated diseases including graft-versus-host disease (GvHD), multiple sclerosis and rheumatoid arthritis.