Probable lysosomal thiol reductase that can reduce protein disulfide bonds (By similarity). Involved in the immune response to bacterial infection (PubMed:24491521). Up-regulated following injection with the Gram-negative bacterium E.coli. Up-regulation increases between 1 and 12 hours after the injection, then decreases between 12 and 48 hours, and then increases again at 72 hours. RNAi-mediated knockdown in the fat body or hemocyte of flies infected with the Gram-negative bacterium E.coli results in an increase in bacterial load 24 hours after infection. Belongs to the GILT family.