Class I Antigen Expression in Line 1 Cells: Molecular Biology and Immunological Effects

Abstract

Cultured line 1 murine lung carcinoma cells normally express very low levels of class I H-2 antigens. We have continued our investigations of line 1 lung carcinoma cells to understand the molecular basis of decreased expression of class I H-2 antigens and class I antigen induction with dimethyl sulfoxide (DMSO). We show that line 1, a murine lung carcinoma cell line, has low levels of class I antigens (H-2K, D, and L) because it is deficient in both class I and beta2-microglobulin (B2M) RNAs, and tha. the mRNAs can be coordinately induced with dimethyl sulfoxide (DMSO). Our experiments suggest that interferon can induce surface expression of class I antigens but may act through a different mechanism than DMSO in inducing class I antigens. To further evaluate the regulation of class I expression, H-2Dp genes were transfected into line 1 cells. The transfected H-2 genes appear to be constitutively expressed at much higher levels than are the endogenous class I genes and are associated with endogenous B2M protein. Surface expression of the DP antigens on the transfectants is induced similar to the endogenous H-2d haplotype class I antigens following treatment with DMSO. All the DP transfectants had increased levels of B2M mRNA as well as higher levels of class I RNA when compared to control or untransfected line 1 cells. These results suggest that the regulation of class I and B2M genes is linked and that expression of class I genes can affect expression of B2M genes.