Mouse CD40-transfected cell lines cannot exhibit the binding and RANTES-stimulating activity of exogenous heat shock protein 70

CD40 in Endothelial Cells Restricts Neural Tissue Invasion by Toxoplasma gondii

Little is known about whether pathogen invasion of neural tissue is affected by immune-based mechanisms in endothelial cells. We examined the effects of endothelial cell CD40 on Toxoplasma gondii invasion of the retina and brain, organs seeded hematogenously. T. gondii circulates in the bloodstream within infected leukocytes (including monocytes and dendritic cells) and as extracellular tachyzoites. After T. gondii infection, mice that expressed CD40 restricted to endothelial cells exhibited diminished parasite loads and histopathology in the retina and brain. These mice also had lower parasite loads in the retina and brain after intravenous (i.v.) injection of infected monocytes or dendritic cells. The protective effect of endothelial cell CD40 was not explained by changes in cellular or humoral immunity, reduced transmigration of leukocytes into neural tissue, or reduced invasion by extracellular parasites. Circulating T. gondii-infected leukocytes (dendritic cells used as a model) led to infection of neural endothelial cells. The number of foci of infection in these cells were reduced if endothelial cells expressed CD40. Infected dendritic cells and macrophages expressed membrane-associated inducible Hsp70. Infected leukocytes triggered Hsp70-dependent autophagy in CD40⁺ endothelial cells and anti-T. gondii activity dependent on ULK1 and beclin 1. Reduced parasite load in the retina and brain not only required CD40 expression in endothelial cells but was also dependent on beclin 1 and the expression of inducible Hsp70 in dendritic cells. These studies suggest that during endothelial cell-leukocyte interaction, CD40 restricts T. gondii invasion of neural tissue through a mechanism that appears mediated by endothelial cell anti-parasitic activity stimulated by Hsp70.

Lymphoid neoplastic P388D1 cells express membrane protein candidates that discriminate among the C-terminal phylogenetic diversity in heat shock protein 70 sequences

We previously found that mouse inducible Hsp72 bound more extensively to lymphoblast-like lymphoid neoplastic P388D1 cells than to RAW264.7 monocyte-macrophages. In the present study, we analyzed the characteristics of the binding to P388D1 cells of recombinant HSP70 derived from different species. Recombinant mouse inducible-type Hsp72 bound extensively to P388D1 cells in a saturable manner, but not to P815 mastocytoma or EL4 thymoma. Spinach Hsc70-1, highly homologous with mouse Hsp72 in the C-terminal region, also bound to P388D1 cells. In contrast, significant binding was not observed for bacterial DnaK derived from Lactobacillus acidophilus and Escherichia coli which have relatively little homology in this region. Analyses of surface antigens showed that B220, and CD19, but not CD91, LOX-1, and CD40, the HSP70 receptors reported so far, were present on P388D1 cells, suggesting a B-cell lineage for this cell line. A similar discrimination of the diversity between mouse Hsp72 and bacterial DnaK occurred for CD19(+) B cells derived from mouse spleen, Peyer's patches, and mesenteric lymph nodes. The binding of HSP70 to P388D1 cells was partially, but significantly, antagonized by fucoidan and maleylated BSA, implying a few types of scavenger receptors to be responsible for the binding of HSP70 to this cell line. Furthermore, photo-affinity labeling revealed several membrane protein candidates larger than 110kDa to be involved in the recognition of HSP70 molecules. Using a NF-κB-luciferase reporter assay, we found that exogenous HSP70 did not stimulate NF-κB-dependent signal transduction in P388D1 cells. It thus follows that lymphoid neoplastic P388D1 cells express membrane protein candidates that discriminate among the C-terminal sequences of the HSP70 family. The present results indicate that several types of cells in the innate immune system may distinguish among the phylogenetically specific signals in protein molecules.

Expression of CD40 and CD40L in gastric cancer tissue and its clinical significance

To study expression of CD40 and CD40L in gastric cancer tissue we assessed gastric cancer patients admitted to the Department of Gastroenterology of The First Affiliated Hospital of Soochow University and control subjects. Gastric cancer and normal (from around tumours) tissue samples were obtained from patients. Venous blood samples (gastric cancer and ulcer groups) were drawn on the morning of the day before surgery for the measurement of peripheral sCD40L. The expression of CD40 in gastric carcinoma specimens was examined immuno-histochemically. The clinicopathological factors, including age, sex, tumor size, gross appearance, degree of cellular differentiation, histological classification, depth of tumor invasion, lymph node metastasis, peritoneal dissemination, and TNM stage were analyzed according to the different expression of CD40. The results indicated a high CD40 expression in gastric cancer tissues. This positive expression of CD40 revealed a significant (P < 0.05) correlation with lymphatic metastasis and tumor TNM stage in gastric cancer patients. It is concluded that higher CD40 expression existed in expanding type tumors and could play an important role in clinical diagnosis of gastric cancer patients.

Functional region of mouse heat shock protein 72 for its binding to lymphoid neoplastic P388D1 cells

Extracellular heat shock proteins have been reported to participate in both innate and adaptive immune responses. We have found that recombinant mouse inducible heat shock protein 72 (Hsp72) bound to lymphoid neoplastic P388D1 cells. In the present study, we examined which region of mouse Hsp72 interacted with this cell line by using truncated variants that are sequentially lacking sections of the C-terminal region. The full-length mouse Hsp72 specifically bound to P388D1 cells, but not to mastocytoma P815 cells. Deletion of the C-terminal tail portion of mouse Hsp72 markedly decreased the binding to P388D1 cells and the sequential truncation of the C-terminal helical region led to a loss of binding activity. Specific binding was not observed for either the variant with a minimal substrate-binding structure or the ATP-binding domain alone. On the other hand, two truncated variants lacking the ATP-binding domain significantly bound to P388D1 cells. However, the variant lacking the substrate-binding domain did not show any binding to this cell line. These results suggest that the activity to bind P388D1 cells is attributable to the C-terminal region of mouse Hsp72 in combination with the substrate-binding domain. Interestingly, the binding of mouse Hsp72 to P388D1 cells was competed by the variant with the C-terminal flexible tail sequence, but not by the variant without that sequence. These competitive experiments imply that there may be at least two membrane receptors on P388D1 cells and also that both receptors may recognize the various structures in the C-terminal region of the Hsp70 family for regulation of innate immunity.