CD26. also known as dipeptidyl peptidase-4 (DPP4), is a cell surface glycoprotein with enzymatic and co-stimulatory functions. It cleaves N-terminal dipeptides from substrates, including cytokines, chemokines, and neuropeptides, modulating their bioactivity. Expressed on immune cells (e.g., T cells), epithelial cells, and endothelial cells, CD26 plays roles in T-cell activation, glucose metabolism (via GLP-1 degradation), and immune regulation. Its dual enzymatic and receptor-like properties link it to inflammatory diseases, cancer, and metabolic disorders.
CD26 antibodies target specific epitopes on the protein, either blocking enzymatic activity or interfering with receptor-mediated signaling. Agonistic antibodies enhance T-cell co-stimulation, showing potential in cancer immunotherapy, while antagonistic antibodies inhibit DPP4 activity, mimicking antidiabetic drugs like sitagliptin. In oncology, CD26 is overexpressed in certain cancers (e.g., T-cell lymphoma, prostate cancer), making it a biomarker or therapeutic target. Antibodies labeled with fluorescent dyes or radioisotopes aid in diagnostic imaging.
Research also explores CD26's role in autoimmune diseases (e.g., rheumatoid arthritis) and viral infections (e.g., MERS-CoV entry). Challenges include balancing enzymatic inhibition with immune modulation and managing off-target effects. Ongoing studies aim to refine antibody specificity and therapeutic efficacy, underscoring CD26's multifaceted role in health and disease.