Partial purification and characterization of a novel murine factor that augments the expression of class I MHC antigens on tumor cells

A soluble factor which augments the expression of major histocompatibility complex class I (MHC I) antigens on a number of murine tumor cell lines, has been isolated from the culture supernatants of mixed lymphocyte reaction of spleen cells derived from C57B1/6, Balb/c and Swiss mice. The factor, termed MHC-augmenting factor (MHC-AF) has been partially purified by Sephadex G-100 column chromatography and reverse phase HPLC. MHC-AF activity is associated with an 18 kDa molecule. MHC-AF activity was resistant to pH 2.0 treatment and partially purified MHC-AF preparations did not have any activity in L929 cell/vesicular stomatitis virus (VSV) interferon bioassay system. Antibodies to IFN-gamma did not block the activity of MHC-AF. These results indicate that a MHC-AF distinct from IFN-gamma, is produced by mouse spleen cells undergoing a mixed lymphocyte reaction.

Effect of gamma interferon on the expression of class I MHC antigens on fresh leukemic cells and their susceptibility to lysis by lymphokine activated killer cells.

Relationship between MHC class I antigen expression on PBLs from leukemia patients and their susceptibility to lysis by LAK cells was investigated. LAK cells induced small yet significant lysis of leukemic cells. In nine out of 14 cases studied, treatment with Interferon gamma (200 U/ml for 48 hours) resulted in a decrease in the LAK susceptibility of leukemic cells. In six of these cases, there was a concomitant increase in the expression of class I MHC antigen expression. In three samples, the increase in MHC class I antigen expression was not accompanied by a decrease in LAK susceptibility. IFN treatment had no effect on the binding of leukemic cells to LAK effector cells.