Heat shock proteins form part of a danger signal cascade in response to lipopolysaccharide and GroEL

Abstract

An increasing number of cell types, including peripheral blood mononuclear cells (PBMCs), have been demonstrated to release heat shock proteins (Hsps). This paper investigates further the hypothesis that Hsps are danger signals. PBMCs and Jurkat cells released Hsp70 (0·22 and 0·7 ng/106 cells, respectively) into medium over 24 h at 37°C. Release of Hsp70 was stimulated 10-fold by GroEL (P < 0·001) and more than threefold by lipopolysaccharide (LPS) (P < 0·001). Although Hsp60 could be detected in the medium of cells cultured at 37°C for 24 h, the low rates of release were due probably to cell damage. Significant release of Hsp60 was observed when Jurkat cells were exposed to GroEL (2·88 ng/106 cells) or LPS (1·40 ng/106 cells). The data are consistent with the hypothesis that Hsp70 and Hsp60 are part of a danger signalling cascade in response to bacterial infection.