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Splenic cytotoxic cells recognize surface HSP70 on culture-adapted EL-4 mouse lymphoma cells
E D Ponomarev1, T N Tarasenko, A M Sapozhnikov
1Division of Immunology, Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, 16/10 Miklukho-Maklaya Str., 117871 V-437, Moscow, Russia.
Abstract:
Heat shock proteins (HSPs) are intracellular proteins which function as molecular chaperones. At the same time, translocation of HSPs to the cell surface has been observed in stressed, infected and transformed cells. It seems plausible that surface HSPs may represent molecular targets for recognition and elimination of 'altered' cells by cytotoxic lymphocytes. Previously we demonstrated that EL-4 mouse lymphoma cells growing in vitro express HSPs on their plasma membrane. In this study, we tested the hypothesis that surface HSPs present on EL-4 cells may mediate their recognition and killing by cytotoxic lymphocytes. We have found that susceptibility of culture-adapted EL-4 cells to in vitro lysis by syngeneic and allogeneic splenocytes correlated with the expression of HSP70 on EL-4 cells. Moreover, cytotoxicity was blocked by pretreatment of EL-4 target cells with anti-HSP70 antibody, whereas antibodies to MHC class I molecules and Thy1 did not have such effect. Cytotoxicity against EL-4 lymphoma was not MHC class I-restricted, and was not decreased after depletion of CD8(+) cells from the effector cell population. We conclude that in vitro killing of EL-4 cells is mediated, at least in part, by NK cells via recognition of HSPs present on the surface of tumor cells. Thus, cytotoxic response against EL-4 lymphoma should serve as a good model to study the role of HSPs in anti-tumor immunity.
Insights
Heat shock proteins (HSPs) on tumor cells can be recognized by cytotoxic lymphocytes, particularly NK cells. This study shows surface HSP70 on EL-4 lymphoma cells mediates their recognition and killing, offering a model for anti-tumor immunity research.
Area of Science:
- Immunology
- Molecular Biology
- Oncology
Background:
- Heat shock proteins (HSPs) are intracellular molecular chaperones.
- Translocation of HSPs to the cell surface occurs in stressed, infected, and transformed cells.
- Surface HSPs may serve as targets for cytotoxic lymphocytes to eliminate altered cells.
Purpose of the Study:
- To test if surface HSPs on EL-4 lymphoma cells mediate their recognition and killing by cytotoxic lymphocytes.
- To investigate the role of HSP70 in the recognition and lysis of tumor cells.
Main Methods:
- EL-4 mouse lymphoma cells were cultured in vitro.
- Expression of HSPs on the plasma membrane of EL-4 cells was assessed.
- Cytotoxicity assays were performed using syngeneic and allogeneic splenocytes.
- Blocking experiments utilized anti-HSP70 antibodies and antibodies to MHC class I and Thy1.
- Effector cell populations were manipulated by depleting CD8+ cells.
Main Results:
- Susceptibility of EL-4 cells to lysis correlated with HSP70 expression.
- Pretreatment with anti-HSP70 antibody blocked cytotoxicity.
- Antibodies to MHC class I and Thy1 did not block cytotoxicity.
- Cytotoxicity was not MHC class I-restricted and was independent of CD8+ T cells.
- Natural Killer (NK) cells were identified as the primary mediators of this cytotoxicity.
Conclusions:
- In vitro killing of EL-4 lymphoma cells is mediated by NK cells recognizing surface HSPs.
- Surface HSP70 acts as a crucial target for NK cell-mediated tumor cell lysis.
- This system provides a valuable model for studying HSPs in anti-tumor immunity.