For its cell surface expression, radioprotective 105 (RP105) – an orphan Toll‐like receptor – must form a complex with a soluble glycoprotein called myeloid differentiation 1 (MD‐1). The number of RP105‐negative cells is significantly increased in patients with systemic lupus erythematosus (SLE); however, to elucidate the mechanism underlying this increase, how RP105 is expressed on the cell surface depending on MD‐1 should be investigated. We demonstrated that RP105 exhibits two forms depending on MD‐1 and its two N‐glycosylation sites, N96 and N156. Cell surface expression of RP105 decreased in the presence of mutant MD‐1 (N96Q/N156Q). Nonglycosylated MD‐1 decreased the de novo cell surface expression of RP105 but not pre‐expressed RP105. Thus, the N‐glycans of MD‐1 may represent targets for SLE therapy. [ABSTRACT FROM AUTHOR]