RP105/CD180
RP105, the CD180 antigen encoded by LY64, is a leucine-rich repeat receptor homologous to Toll-like receptors but lacking the intracellular TIR signaling domain. On the surface of B cells it forms a receptor complex with MD-1, and this module cooperates with TLR4 in sensing lipopolysaccharide, regulating the strength and duration of B cell activation responses. RP105 expression is characteristic of mature B cells, with additional presence on monocytes and dendritic cells. Diminished RP105 surface expression on B cells has been documented in systemic lupus erythematosus, linking the receptor to the dysregulated B cell activation characteristic of that disease.
