CD103, also known as alpha E integrin & human mucosal lymphocyte antigen 1, is an integrin protein with expression on intraepithelial T cells & some peripheral regulatory T cells. CD103 is expressed at high levels on tumour-infiltrating FOXP3-positive regulatory T cells in cancer and CD103-positive T cells are strongly associated with patient survival in high-grade serous ovarian cancer.
CD103 expression has been suggested as a definitive marker of intraepithelial, tumour-specific infiltrating lymphocytes. In addition, CD103-positive cells have also been identified in a small proportion of breast cancers.
CD103 is recommended for the detection of specific antigens of interest in normal and neoplastic tissues, as an adjunct to conventional histopathology using non-immunologic histochemical stains.