The monoclonal antibody 2F8 recognizes mouse scavenger receptor class A (SR-A), type I and II, also known as CD204. SR-A belongs to the group of scavenger receptors, which are divided in class A, B, D and E. Class A scavenger receptors (SRs) are multi-domained membrane glycoproteins that can endocytose modified lipoproteins and bind a wide range of ligands. SR-A is expressed by tissue macrophages and functions both as an endocytic receptor for lipoproteins and as an adhesion receptor for macrophages binding to ligand rich tissues e.g. atherosclerotic lesions. Tissue macrophage- populations that express SR-A I and II include those of the marginal zone of the spleen, alveolar macrophages, heart and gut.SR-A binds bacterial pathogens and is considered to play a role in the innate immune response. TLR2 and TLR4 agonists synergistically up-regulate SR-A in RAW264.7 through p38 pathway. SR-A knockout mice are more susceptible to endotoxic shock than wild type mice, which suggests a role in the clearance of bacterial endotoxin from the circulation. Using thymic macrophages of the knockout mice as well as antibody treatment confirmed that SR-A is responsible for half of the phagocytic activity required for apoptotic thymocyte ingestion. Next to its role in innate immunity there is evidence that SR-A also contributes to acquired immune responses.Monoclonal antibody 2F8 recognizes an epitope within the αhelical coiled-coil domain of SR-A in all mouse strain tested, with the exception of C57BL/6. One amino-acid change (L168S), due to polymorphism, results in the loss of reactivity of antibody 2F8.