LL-37 is a cationic and α-helical antimicrobial peptide expressed in human bone marrow, testis, granulocytes, and gingival epithelium and is upregulated in psoriatic lesions. It inhibits growth of Gram-positive E. coli D21 and Gram-negative B. megatarium in a concentration-dependent manner and LL-37 expression is induced in A549 epithelial cells, alveolar macrophages, neutrophils, and monocyte-derived macrophages following M. tuberculosis infection. LL-37 binds sheep erythrocytes coated with S. minnesota Re-LPS and induces agglutination with a minimal agglutinating concentration (MAC) of 12.1 μg/ml. It is a chemoattractant for, and can induce calcium mobilization in, human monocytes, neutrophils, and T cells that naturally express formyl peptide receptor-like 1 (FPRL1) and FPRL1-transfected HEK293 cells. LL-37 (10-15 μM) pretreatment of dengue virus type 2 (DENV-2) reduces its infectivity as well as levels of viral genomic RNA and NS1 antigen. In vivo, LL-37 inhibits cecal ligation and puncture-induced caspase-1 activation and pyroptosis of peritoneal macrophages, reduces levels of the inflammatory cytokines IL-1β, IL-6, and TNF-α, and improves survival in polybacterial septic mice.