Mice immunized with optimal doses of autologous tumor–derived gp96 resist a challenge with the tumor that was the source of gp96. Immunization with quantities of gp96 5–10 times larger than the optimal dose does not elicit tumor immunity. This lack of effect is shown to be an active, antigen-specific effect, in that immunization with high doses of tumor-derived gp96, but not normal tissue–derived gp96, downregulates the antitumor immune response. Furthermore, immunization with fractionated doses of gp96 elicits the same kind and level of response as elicited by a single dose equivalent to the total of the fractionated doses. This is true of  the tumor-protective doses as well as the high downregulatory doses of gp96. The downregulatory activity can be adoptively transferred by CD4+ but not CD8+ T lymphocytes from mice immunized with high doses of gp96. These observations indicate that immunization with gp96 induces a highly regulated immune response that, depending upon the conditions of immunization, results in tumor immunity or downregulation.

Injury causes tissue breakdown, which releases large quantities of intracellular contents into the extracellular space. Some of these materials are well-established activators of the immune system and include heat shock proteins (HSPs), uric acid, nucleotides, High Mobility Group Box-1 protein (HMGB-1), and DNA. Here, we show that in vivo delivery of HSPs into BALB/cJ mice with full-thickness wounds accelerates the rate of wound closure by 60% as compared with control-treated mice. The onset is rapid and the effect is sustained, dose dependent, and protein specific. Adoptive transfer of RAW264 macrophages pretreated with HSP70 into naïve recipients with a wound transfers the HSP-mediated effect on the rate of wound closure. Further, we demonstrate that part of the mechanism by which HSP70 accelerates wound closure is through the stimulation of macrophage-mediated phagocytosis of wound debris. Disabling the HSP70-mediated enhancement of phagocytosis abrogates the HSP-mediated acceleration of the healing process. These findings create two opportunities: one, therapeutic, wherein HSP70 could be used in the clinical management of wounds; and two, pathophysiologic, to decode signals by which the host defenses recognize and respond to injury.

Immunization with heat-shock protein (HSP) gp96 elicits protective immunity to the cancer or virus-infected cells from which it is derived. Low doses of gp96 generate immunity, while doses 10 times the immunizing dose do not. We show here that injection of high doses of gp96 generates CD4(+) T cells that down-regulate a variety of ongoing immune responses. Immunization with high doses of gp96 prevents myelin basic protein- or proteolipid protein-induced autoimmune encephalomyelitis in SJL mice and the onset of diabetes in non-obese diabetic mice. The suppression of immune response can be adoptively transferred with CD4(+) cells and does not partition with the CD25 phenotype. The immunomodulatory properties of gp96 (and possibly other HSP) may be used for antigen-specific activation or suppression of cellular immune responses. The latter may form the basis for novel immunotherapies for autoimmune diseases.

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