CD107a

CD107a, also known as lysosome-associated membrane glycoprotein-1 (LAMP-1), is a cell surface marker used to monitor degranulation in cytotoxic lymphocytes such as natural killer (NK) cells and CD8+ T cells. LAMP-1 is a transmembrane glycoprotein abundant in lysosomes and cytotoxic granules, contributing to lysosome integrity and vesicle trafficking. During activation and degranulation, cytotoxic cells exocytose granules containing perforin and granzymes; the fusion of granule membranes with the plasma membrane transiently exposes LAMP-1 on the cell surface, where it can be detected by antibodies.

Surface CD107a expression peaks within minutes after stimulation and decays over hours, making it a dynamic functional readout of degranulation rather than a static marker of cytotoxic potential. Measurement is typically performed by flow cytometry after brief stimulation with target cells or pharmacologic agents, often in combination with intracellular cytokine staining (for example, IFN-γ) to profile polyfunctional responses. CD107a assays are used in basic immunology research and in clinical settings to assess NK cell and cytotoxic T cell function, including applications in cancer immunotherapy, viral infections, transplantation, and suspected immunodeficiencies such as familial hemophagocytic lymphohistiocytosis (HLH).

CD107a refers specifically to LAMP-1; CD107b (LAMP-2) is a related marker used similarly. While LAMP-1 has roles in lysosome biology beyond degranulation, the surface appearance of CD107a serves primarily as a practical indicator of degranulation activity rather than a direct measure of cytotoxic molecule content.