Major histocompatibility complex class II (Ia-like) antigens on chicken embryo fibroblasts: effect of transformation by Rous sarcoma virus.

In this study, three monomorphic monoclonal antibodies to chicken MHC class II molecules (B-L) were tested for reactivity in normal and RSV-transformed embryo fibroblasts. The immunocytochemical staining, the cell-bound ELISA assay, and the immunoprecipitation analysis showed that all three antibodies reacted with the B-L (Ia-like) molecules on normal cells of different genotypes. Conversely, the expression of these antigens was not detected in fibroblasts cultured from feather follicles of adult birds. The level of expression of B-L molecules as well as the class II specific RNA increased consistently after transformation of the cells by the SR-RSV and infection with the avian leukosis virus RAV-1. Analysis of genomic DNA by the Southern blot technique, performed after digestion with several restriction endonucleases, showed that the restriction pattern of B-L genes was not altered in cells transformed by Rous sarcoma virus.

Inhibition of HLA class I antigen and mRNA expression induced by Rous sarcoma virus in transformed human fibroblasts.

Cells from various human nonlymphoreticular neoplasms show reduced HLA class I antigen expression. In this report, a system of human fibroblasts transformed by an avian retrovirus has been employed to investigate the mechanism of this phenomenon. Rous sarcoma virus has been used to transform in vitro human dermal fibroblasts, and clonal cell lines have been established from these cultures. In all the clones studied the integration of the provirus induced a reduction of cell-surface HLA-A, -B, -C framework antigen and beta 2-microglobulin expression when compared to levels for the respective parental fibroblasts. The reduction was correlated with a diminished intracellular synthesis of these molecules. Uninfected cells derived from an osteogenic sarcoma exhibited a reduced expression comparable to that of dermal diploid fibroblasts obtained from the same donor and transformed by Rous sarcoma virus. RNA gel blot analysis of total cellular RNA and of poly(A)+ cytoplasmic RNA showed a markedly decreased amount of HLA class I transcripts in the transformed cells. Southern blot study of genomic DNAs digested with several restriction endonucleases showed that the banding patterns of the HLA genes were not altered in the cells harboring the Rous sarcoma provirus. Our data are consistent with the hypothesis that the Rous sarcoma provirus that does not seem to be linked to the major histocompatibility complex class I gene superfamily may negatively control HLA gene expression.

Expression of major histocompatibility complex antigens (H-B) on haemopoietic cells, lymphoid cells, and chick embryo fibroblasts from congenic lines of chickens.

The expression and distribution of chicken major histocompatibility antigens (H-B) was examined by electron microscopy. Using an indirect method of ferritin and peroxidase labelling with monospecific heteroantisera and with monoclonal antibodies, the H-B alloantigens could be localized at the plasma membrane of various cell types. The antigenic binding sites were quantified on mature erythrocytes, erythropoietic cells, heterophils, lymphoid cells of both thymus and bursa origin, and on cultured normal and Rous sarcoma virus-transformed chick embryo fibroblasts. The degree of labelling was higher in mature normoblastic erythrocytes and lymphoid cells than in other haemopoietic cells and fibroblasts when the heterospecific antisera were used. A larger number of antigenic binding sites was labelled by the monomeric monoclonal antibodies than by the polyclonal antisera. The distribution and aggregation of the specific label on the plasma membrane of cells other than erythrocytes, however, differed in the fixed and unfixed cells.

Reduced expression of MHC class I antigens in chicken fibroblasts transformed by Rous sarcoma virus.

Monoclonal monomorphic as well as polyclonal antibodies against H-B class I (B-F) antigen were used to evaluate the expression of these molecules on normal and RSV-transformed chick embryo fibroblasts. The results indicate that chicken fibroblasts transformed in vitro by the Schmidt-Ruppin strain Rous sarcoma virus of subgroup B (SR-RSV-B) present reduced H-B class I antigen expression as compared to uninfected cells of the same inbred strain. This quantitative reduction was observed at the cell membrane and in whole cell lysates. Chick embryo fibroblasts infected with avian leukosis virus RAV-1 show that the levels of H-B class I antigens were indistinguishable from the levels measured on the control cells. Normal embryo fibroblasts derived from the inbred lines B4/B4 express higher levels of H-B antigens than normal cells carrying the B12/B12 genotype.

[Changes of the expression of histocompatibility (HLA) antigens in human fibroblasts transformed by the avian leukosis-sarcoma virus]. / Modification de l'expression des antigènes d'histocompatibilité (HLA) dans des fibroblastes humains transformés par le virus de la leucosarcomatose aviaire (ASV).

Monoclonal monomorphic antibodies anti-HLA class I and II antigens, were used to evaluate the expression of these molecules on normal and RSV-transformed human fibroblasts. The results indicate that the human diploid fibroblasts transformed in vitro by RSV present a reduced HLA-class I antigens expression as compared to the uninfected fibroblasts of the same donor. In parallel, it is demonstrated that the class II molecules absent on normal cells are expressed after transformation.