Brain-Derived Heat Shock Protein 70-Peptide Complexes Induce NK Cell-Dependent Tolerance to Experimental Autoimmune Encephalomyelitis

Abstract

Heat shock proteins (Hsp) are markedly up-regulated at sites of inflammation during autoimmune diseases like experimental autoimmune encephalomyelitis (EAE). In this study, we show that Hsp70-peptide complexes (pc) isolated from brains of mice with EAE prevented the development of EAE clinically and pathologically when administered before proteolipid protein 139–151 (PLP139–151) immunization. In contrast, pure Hsp70 or Hsp70-pc derived from brains of healthy mice or other inflamed tissue did not modulate the expression of EAE. In animals in which EAE had been suppressed by Hsp70-pc, lymphocytes showed increased cell death in response to PLP139–151 that correlated with elevated IFN-γ and NO production. Coculture of spleen cells from Hsp70-pc immunized mice with spleen cells from untreated EAE mice, in addition to depletion experiments, showed that NK cells reduced reactivity to PLP139–151. Transfer of NK cells from Hsp70-pc-immunized mice to recipients sensitized for EAE abolished disease development. Thus, we propose that Hsp70 demonstrate the ability to bind to peptides generated during brain inflammation and to induce a regulatory NK cell population that is capable of preventing subsequent autoimmunization for EAE.

EAE Tolerance Induction with Hsp70-Peptide Complexes Depends on H60 and NKG2D Activity

“…Searching for mechanisms of immune regulation, we have assessed the role of induction of stress-related peptides at sites of inflammation. In our previous study (21), we showed that a peptide fraction, isolated from EAE brain tissue and chaperoned by the stress-induced protein heat shock protein 70 (Hsp70-pc), induced a state of tolerance through the induction of regulatory NK cells. In this study, we investigated the role of H60 and the NKG2D receptor in the Hsp70-pc-induced inhibition of EAE.…”

“…Hsp70 preparations were isolated and purified according to previously published protocols (21,22). In brief, CNS tissue was homogenized, centrifuged, and loaded on PD10-column.…”

“…Six-week-old SJL/J or C57BL/6 female mice were injected with Hsp70-pc or Hsp70 preparations at dose 1.2 mg/kg, subcutaneously on day 0 and day 7, as described previously (21). On day 14, EAE was induced with PLP 139 -151 (for SJL/J) or MOG (for C57BL/6) peptides in CFA (Difco Laboratories) enriched with 0.75 mg of Mycobacterium tuberculosis.…”

“…The mechanism of Hsp70-pc-induced inhibition of EAE in SJL/J mice was dependent on NK cell function and the protection of EAE was transferred with NK cells from Hsp70-pc preinjected mice (21). Therefore, we decided to search for NK cell activating ligands that could potentially stimulate NK cells in Hsp70-pc preinjected mice.…”

Mechanisms of autoimmunity in the central nervous system: Disturbance of natural autoimmunity, infectious agents, cell contribution and antibody signatures

“…48 However, there are also contradicting findings regarding the contribution of HSP to MS onset. 49 Defective expression of HSP has been suggested to contribute to the neurodegenerative phenomena observed in longterm MS. 50 By contrast, it has been shown that HSP70 binds MBP and proteolipid protein (PLP) peptides, generating immunogenic complexes that might be able to trigger autoimmune responses in mouse models of MS. 51 Similarly, molecular mimicry between bacterial and mammalian HSP has been implicated in the pathogenesis of MS. 52 This suggests that upregulation of key antigens; for instance, the HSP70 might increase the susceptibility to CNS autoimmune disease onset. Therefore, it is not meaningless to suggest that HSP, MOG and others might constitute key antigens from the CNS that are early recognized by the immune system during brain structuring.…”