The chaperonins are a subgroup of oligomeric molecular chaperones; the best-studied examples are chaperonin 60 (GroEL) and chaperonin 10 (GroES), both from the bacterium Escherichia coli. At the end of the 20th century, the paradigm of chaperonins as protein folders had emerged, but it is likely that during the 21st century these proteins will come to be viewed as intercellular signals. Indeed, it is possible that the chaperonins were among the first intercellular signalling proteins to evolve. During the past few years, it has emerged that chaperonin 10 and chaperonin 60 can be found on the surface of various prokaryotic and eukaryotic cells, and can even be released from cells. Secreted chaperonins can interact with a variety of cell types, including leukocytes, vascular endothelial cells and epithelial cells, and activate key cellular activities such as the synthesis of cytokines and adhesion proteins. Much has been made of the high degree of sequence conservation among the chaperonins, particularly in terms of the immunogenicity of these proteins. However, different chaperonin 60 proteins can bind to different cell-surface receptors, including the Toll-like receptors, suggesting that this family of proteins cannot be treated as one biological entity and that several subfamilies may exist. Chaperonins have been implicated in human diseases on the basis of their immunogenicity. The finding that chaperonins can also induce tissue pathology suggests that they may play roles in infections and in idiopathic diseases such as atherosclerosis and arthritis.

An infection approach was adopted for examining consequential heat shock (HS) or stress response in brain and spleen tissues from Wistar rats. Stress in this system was due to interactions with the infecting helminth, Trichinella spiralis, or its body-dwelling larval stages, or products thereof. It was argued that in the infection model used, elements effecting stress in the brain would differ from those in the spleen. HS responses were measured by quantitation of 4 levels of HS proteins (HSP25, HSP60, HSP70 and HSP90) with time, in infected and uninfected rat tissues using an assay depending on immunoblotting specifically to detect the separate HSPs and image analysis to measure HSP content. In brain and spleen tissue from uninfected rats, a continuous expression of the above HSPs was observed at levels which hardly varied throughout the experiment. In contrast, HSP25, HSP60 and HSP70 levels in infected rat tissues varied and apparently depended on ‘infection cycle’-related events. Thus, an enhanced expression of HSP25 and HSP60 and of these plus HSP70 was observed at certain, yet different, time-points during infection in rat spleen and rat brain, respectively. Interestingly, HSP90 expression in spleen tissue from infected rats versus controls, was significantly reduced throughout the experiment suggesting some important (as yet undefined) role for HSP90 in the infection cycle. These studies seem to have provided evidence for the occurrence of soluble factors causing altered HSP expression at both sides of the blood-brain barrier in rats with a primary T. spiralis infection.