Monophosphoryl lipid A (MPLA), also known as Glucopyranosyl lipid A, is an agonist of toll-like receptor 4. Derived from the cell wall of nonpathogenic Salmonella, MPLA is a valuable compound for research on immunization and vaccine development.

Monophosphoryl lipid A, at a concentration of 100 µg/ml for 2 hours, induces NF-κB activation and modulates TLR2 in dendritic cells, as evidenced by Western Blot Analysis. The same compound, ranging from 5 to 100 µg/ml over 24 hours, stimulates IL-12 production in human dendritic cells. Furthermore, increasing Monophosphoryl lipid A levels from 0.1 to 1 µg results in a higher percentage of matured bone marrow-derived dendritic cells (BMDCs). It also enhances cell surface markers on dendritic cells and boosts T cell responses, including the upregulation of calcium mobilization in activated CD4 T cells.

The synthesized Monophosphoryl lipid A activates antigen-presenting cells (APCs) and amplifies the production of Th1- and Th2-specific immune responses in mice[2].