Atherosclerosis is a chronic inflammatory disease and autoimmune mechanisms may contribute to its pathogenesis. Hsp27, a member of the small heat shock protein family, has been found to be expressed in atherosclerotic lesions. The aim of this study was to investigate whether Hsp27 may be involved in atherogenesis. In vitro, Hsp27 treatment of the J774. 2 murine macrophage cell line was associated with a significant decrease in macrophage interleukin (IL)-10 secretion (p < 0.05). This effect was reduced when cells were pretreated with anti-toll like receptor-2 (TLR2) blocking antibodies. Also, a significant increase in macrophage TLR-2 surface expression was observed following treatment with Hsp27 (p < 0.05). In patients with an acute myocardial infarction, Hsp27 concentrations were lower in samples taken 12 hours post-infarction compared to samples taken on admission (p=0.02). There was also a concomitant decrease in the levels of anti-Hsp27 immunoglobulin (Ig)M antibodies (p=0.02) and complement C3 in the 12 hour samples compared to samples taken on admission (p=0.02). In a study group of young healthy controls and gymnasts, for the healthy controls only, there was a divergent association between Hsp27 antibody levels with physical activity, with Hsp27 IgM positively correlated (r=0.42, p < 0.05) and the Hsp27 IgG negatively correlated (r=-0.43, p < 0.05) with physical activity. In patients with glucose intolerance (GI) and established cardiovascular disease (CVD) there was a significantly higher serum Hsp27 (p=0.02) concentration, and a significantly lower anti-Hsp27 IgM antibody level (p=0.02), compared to levels in healthy controls and a borderline significantly higher anti-Hsp27 IgG antibody levels compared to levels in GI patients without CVD. Serum anti-Hsp27 IgG antibody levels were positively correlated with levels of the inflammatory marker, intercellular adhesion molecule (ICAM)-1, r=0.28, p=0.03. The pattern of high serum Hsp27, low IgM and high IgG autoantibodies in patients with cardiovascular disease and the association of the Hsp27 IgG antibodies with the inflammatory marker ICAM-1 suggest involvement of Hsp27 in atherogenesis. One way it may support lesion development is via its inhibitory action on macrophage production of the inflammatory cytokine, IL-10.