Clinical immunology and immunopathology最新文献

Insulin-like growth factor-I (IGF-I) is a polypeptide mitogen which is regulated by growth hormone (GH). IGF-I mediates many of the biological functions of GH, including the maintenance of lymphoid mass and functions. Since GH secretion declines with age, we asked whether changes in the availability of IGF-I might contribute to age-associated alterations in immune functions. As a first step, we examined relationships between plasma levels of IGF-I andin vitrocorrelates of immunity in young and elderly subjects. Heparinized plasma and lymphocytes were collected from the peripheral blood of 34 healthy young (aged 27 ± 0.9 years, mean ± SEM) and 41 elderly (79 ± 1.3 years) volunteers (31 males and 44 females in total). Plasma levels of IGF-I, measured by radioimmunoassay after the removal of IGF-I-binding proteins, were reduced among elders compared to young controls (138 ± 8.7 ng/mL vs 80.2 ± 4.7 ng/mL,P< 0.001). The number of circulating lymphocytes did not change with age. The proliferative response ([³H]thymidine uptake into DNA) of T-cells to concanavalin A and B-cells to pokeweed mitogen were reduced among elders (P< 0.05). An increased spontaneous antitumor natural killer (NK) activity (P< 0.001) was accompanied by a higher percentage of CD16⁺NK cells among lymphocytes in older subjects (P< 0.001). The NK cell number was positively related to IGF-I levels in young volunteers but not among elders. Correlation analysis demonstrated a highly significant relationship between plasma IGF-I levels and T-cell (but not B-cell) proliferative response during aging (r= 0.492,P< 0.001). Our results imply that reduced immunocompetence may be one of the consequences of reduced IGF-I levels in human aging. Among the three types of immune cells tested, the T-cells were most sensitive to fluctuations in IGF-I levels. Reduced IGF-I availability may be one of the determinants of the decline in T-cell-mediated immune function in the elderly. To our knowledge, this is the first report presenting correlative data on concurrent changes in IGF-I levels and immune parameters in human aging.

Modulation of CD8⁺T-cell responses specific for an exogenous antigen by epitope variants would be advantageous to develop a novel means of antigen-specific immune regulation. We have analyzed CD8⁺T-cell responses to single amino acid-substituted variants of a peptide corresponding to residues 142–149 (p142-149; LAYFYPEL) of α_s1-casein, a major milk allergen, which is a dominant determinant restricted by H-2K^b. An analog peptide L142I with a substitution of Ile for Leu at the nonanchor N-terminal residue induced more IFN-γ secretion than p142-149 from specific CD8⁺T cells. Furthermore, L142I could prime CD8⁺T cells more efficientlyin vivo,and these L142I-primed cells secreted more IFN-γ than p142-149-primed CD8⁺T cells upon stimulation with p142-149in vitro.These findings are mainly explained by the greater ability of L142I to form stable K^b–peptide complexes. These findings indicate that appropriate analog peptides may be useful as efficient inducers of CD8⁺T cells which recognize the parent peptide and secrete IFN-γ, a potent inhibitor of Th2-dependent events, including IgE production.

We previously reported that intramuscular (i.m.) immunization of DNA vaccine encoding human immunodeficiency virus type 1 (HIV-1)_IIIBenvandrevgenes alone or in combination with appropriate adjuvant induces substantial and enhanced immune response against HIV-1. In the present study, we examined whether a polymer, low-viscosity carboxymethylcellulose sodium salt (CMCS-L), has an adjuvant effect on immune response induced by DNA vaccination. BALB/c mice were immunized with HIV-DNA vaccine formulated with CMCS-L via the intranasal (i.n.) and i.m. routes. The combination with the polymer elicited higher levels of antigen-specific serum IgG and fecal IgA antibodies than DNA vaccine alone. For cell-mediated immunity, HIV-specific delayed-type hypersensitivity response and cytotoxic T lymphocyte activity were measured by the footpad-swelling test and the⁵¹Cr-release assay, respectively. Both were enhanced by the combination with CMCS-L via i.n. and i.m. inoculation. Cytokine analysis in culture media of bulk splenocytes harvested from immunized animals showed higher levels of IL-4 production in i.n.-immunized mice compared with i.m.-immunized mice. Nevertheless, the increased IFN-γ production resulting from the combination with CMCS-L was observed only in i.n.-immunized mice. These data indicate that i.n. immunization of HIV-DNA vaccine formulated with CMCS-L enhances HIV-specific mucosal antibody (Ab) and systemic Ab and cell-mediated immune response.

The early events of activation and cytokine profiles (IL-2, 4, and 6) were studied in lymphocytes of paucibacillary (TT/BT) and multibacillary (BL/LL) leprosy patients after stimulation with PMA/A23187 andMycobacterium lepraeantigen (PGL-1). Lymphocytes from BT/TT patients showed proliferation in response to both PMA/A23187 and PGL-1 compared to BL/LL. The levels of early activation signaling molecules such as IP₃, calcium, and protein kinase C (PKC) in the particulate fraction were found to be elevated in BT/TT and BL/LL patients and showed a further significant increase after stimulation with PMA/A23187 in BT/TT patients. PGL-1 marginally increased the IP₃levels in BT/TT patients, whereas in BL/LL patients, it had no effect. The levels of IL-2 were enhanced in lymphocytes of BT/TT leprosy patients and were further augmented by PPD and PGL-1, while the levels of IL-4 and IL-6 were increased in LL/BL lymphocytes and further augmented by PGL-1. Thus PGL-1 seems to be a major culprit in inducing the T_H2-type cytokine response observed in lepromatous leprosy patients.

To examine the possibility of immunotherapy for activating liver-associated mononuclear cells (liver MNC) in hepatocellular carcinoma (HCC), we evaluated the cytotoxicity of liver MNC and peripheral blood mononuclear cells (PBMNC) in HCC patients and examined how they can be activated by cytokines and how this activation is modulated by reduction/oxidation. Cytotoxicity of liver MNC but not PBMNC in HCC patients was significantly decreased compared with that of controls, despite no alteration in the subpopulation of liver MNC between the two groups. We next measured intracellular glutathione (GSH), which is required for the enhancement of the cytotoxicity by interleukin-2 (IL-2). Intracellular GSH levels of liver MNC in HCC were significantly lower than that of controls.In vitroadministration ofN-acetylcysteine (NAC) not only restored intracellular GSH levels but also enhanced the IL-2-stimulated cytotoxicity of liver MNC in HCC patients. This suggests that intracellular GSH of liver MNC in HCC may participate in the modulation of cytotoxicity of liver MNCin vitroand that NAC may be effective as an adjunct to immunotherapy for HCC.

To evaluate the oxidative burst in hepatitis C virus (HCV) infection, intracellular hydrogen peroxide (H₂O₂) production of polymorphonuclear (PMN) cells isolated from 15 chronic HCV-infected patients and 11 controls was assessed by flow cytometry in a time kinetic. Under nonstimulated and phorbol myristate acetate (PMA)-stimulated conditions, H₂O₂production was higher in HCV-infected patients than in controls (P<0.05) at the time points of 20, 30, and 40 min. A positive correlation between H₂O₂production by PMA-stimulated cells and serum levels of alanine aminotransferase and aspartate aminotransferase was found in the HCV-infected patients (r= 0.877,P<0.01 andr= 0.9351,P<0.001, respectively). RT-PCR analysis of purified mononuclear (MN) and PMN cells from HCV-infected patients revealed the presence of HCV RNA in 60% of MN and 27% of PMN cell samples. These results suggest that a functional alteration of PMN cells is manifested in this chronic viral infection which may represent an additional factor in the development of liver lesions.

Although the etiology of sarcoidosis is still unknown, it is now clear that the formation of the sarcoid granuloma is keenly regulated by a cascade of cytokines. Furthermore, several experimental data indicate a direct association between the release of cytokines and the development of lung fibrosis. In a recent meeting over 300 investigators convened to assess current knowledge in the field of sarcoidosis, vasculitis, and diffuse lung diseases. The meeting provided an overview on the complex networks between immunocompetent cells, cytokines, and mesenchymal cells setting the stage for the pathogenesis of granulomatous and vasculitic disorders. However, emphasis was given to the possibility of using innovative immunotherapies to target relevant cytokines or molecules involved in granuloma formation and the remodelling of lung tissue.

The nonintegrin receptor CD26, also known as dipeptidyl peptidase IV (DPP IV) is a transmembrane 110- to 120-kDa serine aminopeptidase glycoprotein with multiple functions, including cellular trafficking through extracellular matrix, and costimulatory potential during T cell activation, and is an influence upon T cell differentiation during their maturation in the thymus. In order to further define the expression and functional activity of this membrane exopeptidase in human thymus, we utilized a nondisruptive, cytofluorogenic assay which allowed simultaneous measurement of intracellular DPP IV activity using a fluorochrome-conjugated peptide substrate with surface staining of plasma membrane-associated T lymphocyte lineage antigens CD4 and CD8, as well as CD26. Human thymi were examined using the three-color assay, and significant differences in time-dependent DPP IV activity were found among the thymocyte subsets defined by their CD4/CD8 phenotype. In this regard, CD4⁻/CD8⁻thymocytes displayed the lowest DPP IV activity and had higher activity than the smaller-sized CD26⁺cells. Thymocytes containing greater percentages of apoptotic cells expressed lower DPP IV activity than viable cells. Thus, DPP IV appears to be upregulated as thymocytes mature and is reduced among thymocyte populations enriched for cells undergoing programmed cell death, suggesting that CD26-associated enzymatic activity is ontogenically controlled during T cell maturation and may be involved in thymic deletion of emerging clones.

Antigens coated with split products of C3, the result of complement activation, are capable of crosslinking the complement receptor 2 (CR2, CD21) and the antigen receptor on the surface of B cells simultaneously. This dual recognition leads to increased cell proliferation and differentiation and enhanced antibody production. CR2 is also considered to be a regulator of the B cell response to antigen. In this review we summarize the biology of the CR2 and focus on its essential role in generating an effective B cell response to antigenic stimuli. The involvement of CR2 in the pathophysiology of infectious and autoimmune diseases is also discussed.

To clarify the roles of increased apoptosis and cell proliferation in chronic autoimmune lymphocytic thyroiditis and thyroid tumorigenesis, expression of p53 and p21^WAF1proteins was immunohistochemically investigated in a series of 158 cases. Positive epithelial cells were quantified to give numbers per unit square and to score for distribution. They were found scattered in nontumorous thyroid tissue, their numbers increasing with the severity of thyroiditis and the correlation between expression of the two proteins, regardless of the presence or absence of thyroid neoplasms. Simultaneous expression of both proteins was occasionally found in the same cells by analysis of serial histologic sections. In thyroid tumors, increased expression was found to be diffuse, focal, or scattered for the distribution of p53- or p21^WAF1-immunopositive cells in accordance with tumor cell dedifferentiation, showing significant correlation between expression of the two proteins. Correlated with these findings, enhanced apoptosis along with decreased Bcl-2 expression and increased Ki-67 labeling in lymphocytic thyroiditis and thyroid tumors was also confirmed in the same series, usingin situDNA nick-end labeling and immunohistochemical methods. Increased expression of p53 and/or p21^WAF1proteins was thus suggestive of possible DNA damage and increased apoptosis in autoimmune thyroiditis. In addition, a significant correlation between protein overexpression and dedifferentiation of thyroid tumor cells was apparent.