Neural cell adhesion molecule expression on renal interstitial cells.

BACKGROUND: At early stages of kidney development, the neural cell adhesion molecule (NCAM) is highly expressed on cells of the metanephrogenic mesenchyme. During maturation of the fetal kidney, NCAM gradually disappears. So far, it has been widely accepted that NCAM in the adult kidney is only expressed by nerves, and not by other cell types. METHODS: NCAM expression was analysed in human adult healthy and diseased kidneys by immunohistochemistry and western blot analysis. NCAM+ renal interstitial cells were further characterized by double immunofluorescent staining using antibodies against neurofilaments, alpha smooth muscle actin, vimentin, alpha5beta1 integrin, CD68, CD11c, HLA-DR and the potential progenitor cell markers CD34, CD117, CD133, CD24, nestin and cadherin-11. RESULTS: In adult human kidneys, NCAM expression is restricted to rare interstitial cells with dendritic morphology, which are neurofilament-negative and predominantly localized on the corticomedullary junction. They are also negative for fibroblast cell markers, but co-express the haematopoietic stem cell markers CD34 and CD133. The number of NCAM+ interstitial cells increased in the initial phases of interstitial fibrosis. Western blot analysis of renal tissues with incipient interstitial fibrosis tissues showed the expression of the 140 kDa NCAM isoform. CONCLUSIONS: These data indicate that a rare subpopulation of NCAM+ interstitial cells could represent renal progenitors, and that NCAM+ interstitial cells can participate in the initial phase of interstitial fibrosis.

Expansion of peripheral CD8+ CD28- T cells in response to Epstein-Barr virus in patients with rheumatoid arthritis.

OBJECTIVE: To investigate control of Epstein-Barr virus (EBV) infection in rheumatoid arthritis (RA) by comparing the frequency phenotypes and function of peripheral CD8+ EBV-peptide antigen-specific T cells in patients with RA and healthy longterm carriers of EBV. METHODS: The frequency of interferon-g (IFN-g)-producing HLA-A2 or HLA-B8-restricted EBV-reactive CD8+ T cells in peripheral blood mononuclear cells (PBMC) from 49 RA patients and 26 healthy EBV carriers was evaluated in Elispot assays with 12 lytic/latent peptide epitopes. Direct staining with HLA-peptide tetramers containing 3 of these peptides was performed for comparison. The phenotype and function of these T cells was determined by FACS and cytotoxicity testing. RESULTS: IFN-g production patterns in Elispot assays revealed that EBV-specific CD8+ T cells were directed predominantly against the lytic epitopes A2/GLC and B8/RAK and to a minor extent to all the other lytic and latent epitopes tested, with no significant differences of the frequencies in patients and controls. However, although similar frequencies of CD8+ T cells stained with A2/GLC or B8/RAK tetramers in both groups, the fraction of A2/GLC or B8/RAK-reactive T cells producing IFN-g in response to specific peptide antigen was significantly lower in RA patients than controls. The A2/GLC or B8/RAK tetramer-positive T cells were also substantially enriched in CD28-CD27- T cells of a late-differentiated phenotype in RA patients but not in controls. CONCLUSION: RA patients show clonal expansion of dysfunctional, terminally differentiated CD8+ EBV-specific T cells in their T cell responses to immunodominant lytic peptide EBV epitopes, which could be a sign of specific impairment of virus-host interactions in RA.

Age-associated accumulation of CMV-specific CD8+ T cells expressing the inhibitory killer cell lectin-like receptor G1 (KLRG1).

Large clonal expansions of peripheral CD8+ T cells carrying receptors for single epitopes of CMV and EBV are common in the elderly and may be associated with an immune risk phenotype predicting mortality. Here we show that the frequency of CD8+ T cells expressing the inhibitory killer cell lectin-like receptor G1 (KLRG1), a marker of cells unable to undergo further clonal expansion, was markedly elevated in CD8+ T cells from old donors. Moreover, tetramer staining revealed that the elevated frequency of CMV-specific CD8+ T cells in the elderly was due to an accumulation of cells bearing this dominant negative receptor. The fraction of CMV-specific T cells able to secrete interferon-gamma after specific antigenic stimulation was significantly lower in the elderly than in the young, although the total number of functional cells was comparable. Therefore, the majority of the clonally expanded virus-specific CD8+ cells in the elderly was dysfunctional. Thus, T cell responses are altered in the aged by an accumulation of replicatively senescent dysfunctional T cells carrying receptors for persistent herpes viruses. The presence of clonal expansions of such virus-specific cells may shrink the available repertoire for other antigens and contribute to the increased incidence of infectious disease in the elderly.

An age-related increase in the number of CD8+ T cells carrying receptors for an immunodominant Epstein-Barr virus (EBV) epitope is counteracted by a decreased frequency of their antigen-specific responsiveness.

The aim of this study was to provide a basis for investigating the effects of one very common environmental factor, Epstein-Barr virus (EBV), on age-related changes in the immune system. To this end, the frequency of CD8(+) T cells carrying receptors for an immunodominant EBV lytic epitope was assessed by direct staining with HLA-peptide tetrameric complexes in 19 very old (>87 years) and 12 young (20-40 years) EBV carriers. The frequency of EBV-tetramer-positive cells within the CD8(+) subset was significantly greater in the old compared to the young group (P=0.001). However, the frequency of EBV antigen-specific IFN-gamma producing T cells, as determined by ELISPOT, was significantly lower in the old (P=0.001). Therefore, the absolute number of functional EBV-specific T cells in the elderly and the young was probably similar. These data suggest CD8 clonal expansions in the elderly, resulting in an accumulation of dysfunctional EBV-specific cells which possibly fill the 'immunological space' and could lead to a shrinking of the T cell repertoire for other novel antigens. This may help to explain the increased incidence and case-fatality caused by viruses and intracellular pathogens in the elderly.

Human alpha-defensins HNPs-1, -2, and -3 in renal cell carcinoma: influences on tumor cell proliferation.

The alpha-defensins human neutrophil peptides (HNPs)-1, -2, and -3 have been described as cytotoxic peptides with restricted expression in neutrophils and in some lymphocytes. In this study we report that HNPs-1, -2, and -3 are also expressed in renal cell carcinomas (RCCs). Several RCC lines were found to express mRNA as well as the specific peptides of HNP-1, -2, and -3 demonstrated by reverse transcriptase-polymerase chain reaction, mass spectrometric, and flow cytometric analyses. At physiological concentrations HNPs-1, -2, and -3 stimulated cell proliferation of selected RCC lines in vitro but at high concentrations were cytotoxic for all RCC lines tested. As in RCC lines, alpha-defensins were also detected in vivo in malignant epithelial cells of 31 RCC tissues in addition to their expected presence in neutrophils. In most RCC cases randomly, patchy immunostaining of alpha-defensins on epithelial cells surrounding neutrophils was seen, but in six tumors of higher grade malignancy all tumor cells were diffusely stained. Cellular necrosis observed in RCC tissues in association with extensive patches of HNP-1, -2, and -3, seemed to be related to high concentrations of alpha-defensins. The in vitro and in vivo findings suggest that alpha-defensins are frequent peptide constituents of malignant epithelial cells in RCC with a possible direct influence on tumor proliferation.