Expression of Heat Shock Protein 60 in Normal and Neoplastic Human Lymphoid Tissues.

Abstract

A molecular chaperonin in mammals, heat shock protein 60 (HSP60) is constitutively expressed in the mitochondria at a low level and is rapidly up-regulated under stress. However, the role of HSP60 in the lymphoid tissues has not been well clarified. In the present study, expression of HSP60 was examined by flow cytometry and immunohistochemistry in normal peripheral blood mononuclear cells, reactive lymphoid tissues, and malignant lymphomas. HSP60 was found to be present constitutively at low levels in a fraction of resting T cells and most monocytes. The blastic change upon mitogen stimulation induced HSP60 at much higher levels in more T, B and NK cells. In normal lymphoid tissues, HSP60 was expressed preferentially in the cytoplasm of large-sized lymphoid cells and macrophages in the germinal centers and the interfollicular area.In non-Hodgkin lymphomas strong expression of HSP60 was detected in most cases of diffuse large B-cell lymphoma, follicular lymphoma, and grade 3 and NK/T cell lymphoma. No immunostaining was observed in low grade B-cell lymphomas, including follicular lymphoma, grade 1 and B-lymphoblastic lymphomas. HSP60 immunoreactivity was variable in T-cell lymphomas. Intense expression of HSP60 was observed in Reed-Sternberg cells in all cases of Hodgkin lymphoma.