TUMOR-ASSOCIATED ANTIGEN 90K ACTIVATES MYELOMONOCYTIC CELL-LINE THP-1

90K is a tumor-associated antigen. Using myelomonocytic cell line THP- 1 we determined neopterin production and tryptophan degradation after exposure of cells to 90K in the presence and the absence of interferon -gamma. Interferon-gamma is a well known stimulus for THP-1 cells indu cing e.g. neopterin production and tryptophan degradation. Treatment o f cells with 50 mu g/ml 90K induced significant neopterin formation, a nd the exposure of cells to 90K in addition to 100 U/ml interferon-gam ma amplified neopterin production compared to the sole effect of inter feron-gamma. In parallel, a significant degradation of tryptophan was observed in culture supematants leading to the formation of kynurenine . When the cells were treated with the combination of 90K and interfer on-gamma the degradation of tryptophan was further enhanced. The data demonstrate that tumor-associated antigen 90K interferes with immunoco mpetent target cells and is able to induce a biochemical response in m onocytic cells.