Depressed responsiveness of peripheral blood mononuclear cells to heat-shock proteins in periodontitis patients

The extensive homology between human and bacterial heat shock proteins (HSP s) may play a role in autoimmune reactions in periodontitis. Thus, we quest ioned whether peripheral blood mononuclear cell (PBMC) proliferative respon ses to HSPs are different between periodontitis patients and control subjec ts with gingivitis. The proliferative responses of PBMCs of patients (n = 1 0) and controls (n = 12) to recombinant mycobacterial HSP60 (MycHSP60) and HSP70 (MycHSP70), as well as recombinant human HSP60 (HumHSP60) and HSP70 ( HumHSP70), were investigated. In addition, the proliferative responses to C andida albicans and purified protein derivatives of Mycobacterium (PPD) wer e included. Mean responses to HumHSP60, MycHSP60, and HumHSP70 were signifi cantly lower for patients compared with controls. The responses to MycHSP70 showed a similar trend. However, when Candida and PPD were used as antigen s, there was no difference in responses of the PBMCs between the periodonti tis patients and controls. The level of IFN-gamma in the supernatants of th e cells stimulated with HSPs was lower in the patients compared with contro ls. This concurs with the current hypothesis that periodontitis patients ha ve a depressed Th1 response. Furthermore, we found that with an increasing estimated subgingival bacterial load, periodontitis patients mount a decrea sing immune response to HSPs, while the controls showed a positive correlat ion between these two parameters. From these findings, we speculate that po or reactivity to HSPs may be a susceptibility factor for destructive period ontal disease and may need to be considered in the pathogenesis of this con dition.