INDUCTION OF HUMAN HSP60 EXPRESSION IN MONOCYTIC CELL-LINES

Both bacterial and mammalian heat shock proteins (HSP) are recognized by some T cells, and hsp60 recognition has been implicated in rheumatoid arthritis. We have developed a model to study the induction of hsp60 in human monocytic cell lines. An anti-mycobacterial hsp65 mAb (ML30), cross-reacting with human hsp60 was used to screen 21 human tumor cell lines in Western blot analysis. All T cell and B cell lymphomas constitutively expressed hsp60 protein at moderate to high levels, while little or no hsp60 protein was detected in two monocytic leukemia lines. Moderate to high levels of hsp60 mRNA and protein could be induced in the THP-I monocytic leukemia cell line by heat shock, retinoic acid, interferon (IFN)-gamma or tumor necrosis factor (TNF)-alpha treatment, the highest levels obtained with a combination of IFN-gamma/TNF-alpha. This was also seen using two rabbit anti-hsp60 antisera directed against the N-terminal or C-terminal part of the human hsp60 protein. The determinants detected by the ML30 mAb or the two rabbit anti-hsp60 antisera were not cell surface expressed, as measured with immunofluorescence (FACS) analysis on control cultured or cytokine treated cell lines. This could be a useful model for studies related to the induction of hsp60 in human cells.