Cellular requirements for tumor-specific immunity elicited by heat shock proteins: tumor rejection antigen gp96 primes CD8+ T cells in vivo.

Purified preparations of 96-kDa heat shock proteins (gp96) have been previously shown to elicit tumor-specific immunity to the tumor from which gp96 is obtained but not to antigenically distinct chemically induced tumors. The cellular requirements of gp96-elicited immunity have been examined. It is observed that depletion of CD8+, but not CD4+, T cells in the priming phase abrogates the immunity elicited by gp96. The CD8+ T cells elicited by immunization with gp96 are active at least up to 5 weeks after immunization. Depletion of macrophages by treatment of mice with carrageenan during the priming phase also results in loss of gp96-elicited immunity. In the effector phase, all three compartments, CD4+ and CD8+ T cells and macrophages, are required. Immunity elicited by whole irradiated tumor cells shows a different profile of cellular requirements. In contrast to immunization with gp96, depletion of CD4+, but not CD8+, T cells during priming with whole tumor cells abrogates tumor immunity. Further, ablation of macrophage function during priming or effector phases has no effect on tumor immunity elicited by whole cells. Our results suggest the existence of a macrophage-dependent and a macrophage-independent pathway of tumor immunity. Our observations also show that in spite of exogenous administration, vaccination with gp96 preparations elicits a CD8+ T-cell response in vivo, and it is therefore a useful method of vaccination against cancer and infectious diseases.     

Suppression of immunoglobulin production in human peripheral blood mononuclear cells by monocytes via secretion of heavy-chain ferritin

In vitro antigen stimulation of peripheral blood mononuclear cells (PBMCs) does not induce immunoglobulin (Ig) production. However, pretreatment of PBMCs with l-leucyl-l-leucine methyl ester (LLME) prior to in vitro stimulation removes the suppression of Ig production. In the present study, we attempted to identify the target cells of LLME and determine the mechanisms by which Ig production in PBMCs is suppressed. We found that CD14⁺ monocytes are involved in the suppression of Ig production in PBMCs. Furthermore, we confirmed that heavy-chain ferritin derived from CD14⁺ monocytes suppresses Ig production in PBMCs, possibly through iron sequestration.     

Adrenomedullin in cultured human retinal pigment epithelial cells

PURPOSE: To determine whether adrenomedullin (ADM), a vasorelaxant peptide is produced and secreted by human retinal pigment epithelial (RPE) cells, whether ADM expression is regulated by inflammatory cytokines and a growth factor, and whether ADM has proliferative effects on these cells. METHODS: Production and secretion of ADM by cultured human RPE cells were examined by Northern blot analysis and radioimmunoassay. Regulation of the ADM expression by basic fibroblast growth factor, interferon (IFN)-gamma, tumor necrosis factor-alpha, interleukin (IL)1beta, or all-trans-retinoic acid was studied. In addition, proliferative effects of ADM on human RPE cells were examined by modified 3-(4,5-dimetylthiazol-2-yl)2,5-diphenyltetrazolium bromide (MTT) assay. RESULTS: ADM mRNA was expressed constitutively in all three human RPE cell lines (F-0202, D407, and ARPE-19) examined. Immunoreactive ADM was detected in the cultured media by radioimmunoassay. Sephadex G-50 column chromatography of the cultured medium showed a single peak eluting in the position of ADM-(1-52). Treatment with IFN-gamma or IL-beta increased ADM mRNA levels and immunoreactive-ADM levels in the medium in dose- and time-dependent manners in ARPE-19 cells. Exogenously added ADM increased the number of F-0202 cells and ARPE-19 cells, and the treatment with ADM antibody or ADM-(22-52) (an ADM antagonist) decreased it. CONCLUSIONS: Human RPE cells produced and secreted ADM. IFN-gamma and IL-1beta induced ADM expression in ARPE-19 cells. Furthermore, ADM stimulated proliferation of RPE cells. These results raise the possibility that ADM is related to the pathophysiology of some inflammatory and proliferative ocular diseases.     

Effect of Accessory Cells on Stimulation of Murine T-Cell Leukemia with Antibodies to the CD3/T Cell Antigen Receptor Complex

Stimulation of EL4 and RL  

     

Expression of heat shock protein (Hsp) 70 and Hsp 40 in gastric cancer

Heat shock proteins (Hsp) 70 and Hsp 40 are stress proteins that cooperate as chaperones in mammalian cells. We determined the expression of Hsp 70 and Hsp 40 in 81 gastric cancers. Immunoreactivities to Hsp 70 and Hsp 40 were detected in 67.9 and 22.2% of tumors, respectively. Immunohistochemical analysis showed enhanced Hsp 70 and Hsp 40 expression in gastric tumor tissue, relative to the surrounding normal tissue. Overexpression of Hsp 70 and Hsp 40 was also confirmed by immunoblotting. Among various clinicopathological parameters, low histopathological differentiation was associated with reduced expression of both proteins.     

Heat Shock Protein–Peptide Complexes, Reconstituted In Vitro, Elicit Peptide-specific Cytotoxic T Lymphocyte Response and Tumor Immunity

Heat shock protein (HSP) preparations derived from cancer cells and virus-infected cells have been shown previously to elicit cancer-specific or virus-specific immunity. The immunogenicity of HSP preparations has been attributed to peptides associated with the HSPs. The studies reported here demonstrate that immunogenic HSP–peptide complexes can also be reconstituted in vitro. The studies show that (a) complexes of hsp70 or gp96 HSP molecules with a variety of synthetic peptides can be generated in vitro; (b) the binding of HSPs with peptides is specific in that a number of other proteins tested do not bind synthetic peptides under the conditions in which gp96 molecules do; (c) HSP–peptide complexes reconstituted in vitro are immunologically active, as tested by their ability to elicit antitumor immunity and specific CD8⁺ cytolytic T lymphocyte response; and (d) synthetic peptides reconstituted in vitro with gp96 are capable of being taken up and re-presented by macrophage in the same manner as gp96– peptides complexes generated in vivo. These observations demonstrate that HSPs are CD8⁺ T cell response–eliciting adjuvants.     

Roles of CD4+ and CD8+ cells, and the effect of administration of recombinant murine interferon gamma in listerial infection

Studies were made on the effects of in vivo administration of anti-CD4 mAb, anti-CD8 mAb, or a combination of both mAbs on multiplication of bacteria, the levels of serum transaminases, and mortality in mice infected with Listeria monocytogenes. Results showed that in sublethal infection, CD8+ cells enhanced the peak of bacterial multiplication and liver cell necrosis, and CD4+ cells suppressed CD8+ cell-mediated enhancement. Results also showed that either CD4+ or CD8+ cells were necessary for, and capable of, mediating clearance of the bacteria. CD8+ cells were more efficient than CD4+ cells, but for optimal clearance both were necessary. In lethal listeriosis, treatment of mice with anti-CD8 mAb or a combination of both anti-CD4 and anti-CD8 mAbs, but not anti-CD4 mAb only, protected mice from death by decreasing multiplication of bacteria in the liver and spleen after a peak of approximately 10(8) CFU, and lowering the elevated serum levels of transaminases. These findings indicated that CD8+ cells were responsible for causing irreversible systemic Listeria infection and severe liver necrosis. In lethal listeriosis, administration of rMuIFN-gamma markedly prolonged survival by decreasing multiplication of bacteria and promoting recovery from liver necrosis.     

Clinical features of 89 patients with autoimmune hepatitis in Nagasaki Prefecture, Japan

We examined the clinical characteristics of 89 patients with autoimmune hepatitis (AIH) in Nagasaki Prefecture, Japan, and assessed the usefulness of a provisional scoring system for the diagnosis of AIH proposed by the International Autoimmune Hepatitis Group in 1993. The majority of patients were middle-aged women in their fifties. All patients showed a hepatitic picture. Forty-three patients (48%) had an insidious or chronic onset, while 34 (38%) had an acute onset, and 12 (14%) had liver cirrhosis at presentation. Seventy-nine patients (89%) were positive for antinuclear antibody (ANA), and 5 (6%) were positive for antibody to the hepatitis C virus (anti-HCV). The prognosis was good, with 90% 3-year survival, and most patients responded well to treatment with corticosteroids. The international scoring system was useful for the diagnosis of AIH in most of our patients; the percentages of patients with definite and probable AIH were 48% and 47%, respectively. However, certain factors, such as negative ANA, positive antimitochondrial antibody, concurrent infection with hepatitis B or C virus, and insufficient response to treatment precluded the diagnosis of AIH in some patients. Whether these patients were indeed "true" AIH patients is not clear at present, and further investigation of such patients may be useful for a better understanding of AIH. (Received: June 26, 1998; accepted: Oct. 23, 1998)