Reconstitution of H‐2 class I expression by gene transfection decreases susceptibility to natural killer cells of an EL4 class I loss variant

Abstract

Several reports have suggested that an inverse correlation exists between major histocompatibility complex class I expression and the susceptibility to natural killer (NK)-mediated lysis. For example, the increased class I expression induced by interferon-gamma was always accompanied by an increased resistance to NK lysis. Likewise, class I loss variants were often more NK susceptible than their normal counterparts. To investigate whether the inverse correlation between class I expression and NK susceptibility was fortuitous or whether the class I molecules were directly responsible for this effect we resorted to gene transfection studies. From the murine thymoma line EL4 and H-2Db- and Kb-negative variant S3 was selected. This variant was highly susceptible to NK lysis. S3 was found to have a defect in beta 2-microglobulin gene expression. Therefore, restoration of Db and Kb expression could be achieved by transfection with the beta 2-microglobulin gene. This resulted in a strong decrease in susceptibility to NK lysis to the level of the H-2+ parental EL4. Transfection with class II genes had no effect. Blocking of the class I molecules on the H-2+ cells with anti-H-2b F(ab')2 fragments increased the susceptibility to NK cells to the level of the H-2- variant S3. These data demonstrate that the class I molecules on the targets are directly responsible for regulation of NK susceptibility but the mechanism is not clear. Possibly the class I molecules interfere with the unknown NK target structures.

Reduction in susceptibility to natural killer cell-mediated lysis of human FO-1 melanoma cells after induction of HLA class I antigen expression by transfection with B2m gene.

“…Furthermore, the lack of effect of anti-HLA class I MAb on NK cell-mediated lysis of untransfected FO-l cells indicates that they modulate the extent of lysis by interacting with the target cells and not with the effector cells. The latter conclusion is in agreement with data by Sturmhofel and Hammerling (26). An anti-H-2 class I MAb did not affect the NK cell-mediated lysis of a variant of mouse thymoma EL4 cells which does not express H-2 class I antigens, but enhanced that of the cells which had acquired H-2 class I antigens after transfection with a mouse B2m gene.…”

“…The increase in NK cell-mediated lysis of melanoma cells induced by anti-HLA class I MAb parallels similar results obtained with human T cell lymphomas, breast carcinoma cells (34) and lung small cell carcinomas (5) and with mouse thymoma cells (26). On the other hand, these results are at variance with the lack of effect of anti-MHC class I antibodies on the NK cell-mediated lysis ofhuman (5) and mouse (35) melanoma cells and of human lymphoblastoid cells (27).…”

“…The reduction in the susceptibility to NK cell-mediated lysis of FO-1 cells after incubation with IFN-y is similar to the slight decrease in NK cell-mediated lysis of a cultured B lymphoblastoid cell line after incubation with IFN-y, although the low HLA class I antigen expression did not change (37). These results are at variance with the lack of effect of IFN-'y on the NK cell-mediated lysis of variants of the mouse cell lines EL4 (26) and YAC (46) …”

Natural Killer Cell Mediated Defence Directed Selectively Against Target Cells Lacking MHC Class I Gene Products

“…Sturmhofel and Hammerling [56] selected an H-2 class I deficient line (S3) fromthe murine EL-4 cell line. This variant was found to have a defect in 132m expression and was highly sensitive to NK cell lysis.…”

“…Transfection of class II genes had no effect. Blocking of class I molecules with Fab fragments against class I molecules increased NK sensitivity of EL-4 to the level of the S3 variant [56]. The second example is the transfection of the p2m deficient YAC-l variant A.H-2-with p2m.…”