Lysosomal thiol reductase that can reduce protein disulfide bonds. May facilitate the complete unfolding of proteins destined for lysosomal degradation. Plays an important role in antigen processing. Facilitates the generation of MHC class II-restricted epitodes from disulfide bond-containing antigen by the endocytic reduction of disulfide bonds. Facilitates also MHC class I-restricted recognition of exogenous antigens containing disulfide bonds by CD8+ T-cells or crosspresentation. Dimer; disulfide-linked. N-glycosylated. Sugar chains contain mannose-6-phosphate (By similarity). Synthesized as a 35 kDa precursor which is then processed into the mature 30 kDa form via cleavage of N-terminal and C-terminal propeptides. Processing of the precursor is mediated by multiple lysosomal proteases (By similarity). Mice lacking GILT are deficient in generating major histocompatibility complex class-II-restricted CD4(+) T-cell responses to protein antigens that contain disulfide bonds. Mice are partially protected from Listeria monocytogenes infection, they exhibit reduced bacterial replication in spleen and liver. Bacterial escape from the phagosome is impaired in the macrophages of these mice. Both precursor form and mature form have thiol reductase activity. Belongs to the GILT family. Extended N-terminus.