Heat Shock Protein 72/73 was Expressed Ubiquitously on Follicular Dendritic Cells in Lymphoid Follicles

Abstract

The precise localization of the heat shock protein (HSP) 70 family on follicular dendritic cells (FDC) is not fully understood. The aim of the present study was to clarify the expression of both the inducible and constitutive 72/73kDa HSP 70 protein on FDC. The expression of heat shock protein (HSP) 72/73 on FDC in various lymphoid follicles was investigated. Immunohistochemically, HSP72/73 was detected on FDC in all the lymphoid tissues and showed extensive labeling of the light zone. Immunoelectron microscopy also confirmed that HSP72/73 was located not only diffusely in the cytoplasm but was also dotted in the nucleus of FDC. Although mantle zone lymphocytes and vascular walls in lymphoid follicles were faintly HSP72/73 positive, the germinal center lymphocytes were all negative. Finally, in situ hybridization demonstrated distinctive follicular expression of HSP70 mRNA. These data clearly indicate that HSP72/73 is ubiquitously expressed on FDC, although the significance of HSP 72/73 expression on FDC remains a mystery.