Correlation of class I MHC antigen levels on some human tumor cell lines with susceptibility to LAK cells and performance in cold target inhibition assays.

Relationships between (a) levels of class I MHC antigens, (b) susceptibility to LAK cells, and (c) ability to perform in cold target competition assays were studied using K562, MOLT-4, Raji, Daudi, and HR7 human tumor cell lines. The hypothesis of inverse correlation between class I MHC antigen expression and susceptibility to LAK cells was concurrent with results using K562, HR7, and Daudi cell lines. For Raji cells, IFN-gamma had no effect on the levels of class I MHC antigen but induced resistance to LAK cells, whereas for MOLT-4 cells, enhanced MHC I expression was not accompanied with any change in susceptibility to LAK cells. In competition experiments, all five tumor cell lines were used as competitors as well as targets. Different specificities of competition were observed for different tumor cells. These results indicated that the different tumor cell lines could share one or more target structures recognized by LAK effector cells. IFN-gamma treatment lowered the ability of several tumor cell lines to inhibit target lysis in cold competition assays. Changes in the competition efficacy of tumor cells correlated better with their susceptibility to LAK cells rather than levels of class I MHC antigens.