The absence of β 2-microglobulin in Daudi cells: Active gene but inactive messenger RNA

Abstract

The Daudi cell line is characterized by an absence of HLA antigen on its surface. This has been attributed to a lack of β₂-microglobulin (β₂M) while the heavy chain of HLA is present intracellularly. Karyotype analysis of Daudi cells has shown a deletion involving one of the β₂-microglobulin alleles. It was generally believed that the absence of β₂-microglobulin in that cell line resulted from an absence of expression of the remaining gene. We report here the unexpected finding of a normal amount of β₂-microglobulin messenger RNA in Daudi cells. This was demonstrated by “Northern blot” hybridization with cDNA plasmid clones as a probe. This mRNA, however, when purified by hybridization-selection with β₂-microglobulin plasmid DNA., is unable to function as messenger in protein synthesis and is therefore an inactive mRNA. The finding of a translationally inactive β₂-microglobulin mRNA. provides a new explanation for the absence of β₂-microglobulin and therefore of HLA antigens in Daudi cells.