RTD-1 and RTD-3 have similar antimicrobial activities against the Gram-positive bacteria S.aureus 502A and L.monocytogenes, the Gram-negative bacteria S.typhimurium and E.coli ML35, and the fungi C.albicans 16820 and C.neoformans 271A. RTD-1 is a cyclic heterodimer composed of subunits A and B; disulfide-linked (PubMed:23148585). RTD-3 is a cyclic homodimer composed of two subunits A; disulfide-linked. RTD-1 is expressed in bone marrow. Detected in promyelocytes, myelocytes and mature neutrophils and monocytes. RTD-1 expression begins early during granulocyte myelopoiesis. Forms a cyclic peptide with subunit A (RTD-3) or with subunit B (RTD-1). An additional intersubunit disulfide bond is formed. RTD-1, heterodimer, cyclized and oxidized. RTD-3, homodimer, cyclized and oxidized. RTD-1, heterodimer and reduced. RTD-3, homodimer and reduced. RTD-1 is 10-fold more present in cells than RTD-3. Belongs to the alpha-defensin family. Theta subfamily.