Unique chemotactic response profile and specific expression of chemokine receptors CCR4 and CCR8 by CD4(+)CD25(+) regulatory T cells

Chemokines dictate regional trafficking of functionally distinct T cell subsets. In rodents and humans, a unique subset of CD4(+)CD25(+) cytotoxic T lymphocyte antigen (CTLA)-4(+) regulatory T cells (Treg) has been proposed to control peripheral tolerance. However, the molecular basis of immune suppression and the trafficking properties of Treg cells are still unknown. Here, we determined the chemotactic response profile and chemokine receptor expression of human blood-borne CD4(+)CD25(+) Treg cells. These Treg cells were found to vigorously respond to several inflammatory and lymphoid chemokines. Treg cells specifically express the chemokine receptors CCR4 and CCR8 and represent a major subset of circulating CD4(+) T cells responding to the chemokines macrophage-derived chemokine (MDC)/CCL22, thymus and activation-regulated chemokine (TARC)/CCL17, I-309/CCL1, and to the virokine vMIP-I (ligands of CCR4 and CCR8). Blood-borne CD4(+) T cells that migrate in response to CCL1 and CCL22 exhibit a reduced alloproliferative response, dependent on the increased frequency of Treg cells in the migrated population. Importantly, mature dendritic cells preferentially attract Treg cells among circulating CD4(+) T cells, by secretion of CCR4 ligands CCL17 and CCL22. Overall, these results suggest that CCR4 and/or CCR8 may guide Treg cells to sites of antigen presentation in secondary lymphoid tissues and inflamed areas to attenuate T cell activation.

Lymphocyte expression of human leukocyte antigen class II molecules in patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a multifactorial disorder, deriving from a combination of environmental and genetic factors. Polymorphisms of genes of the human major histocompatibility complex in COPD have been poorly studied in the past. In a preliminary approach, it was difficult to type human leukocyte antigen (HLA) at the protein level and it was hypothesized that there was a reduced surface density of HLA class II molecules. The aims of this study were to analyse, by cytofluorimetry, HLA class I and II molecule densities on peripheral mononuclear cells of COPD patients and to investigate whether there was a correlation with the polymorphisms of DQA and DQB promoter regions which are supposed to be important factors involved in surface expression of HLA-DQ molecules. The study investigated 27 male COPD patients admitted because of disease exacerbation and 49 healthy male controls. Quantitative analysis of fluorescence intensity of HLA class I (A, B, C) and class II (DR, DP, DQ) molecules was performed on blood mononuclear cells by cytoron cytofluorimetry. Polymorphisms of DQA and DQB promoters (QAP and QBP) were determined from the DNA (PCR-SSO). The surface densities of HLA class I and HLA-DQ molecules did not differ between the COPD patients and controls. HLA-DP molecule density seemed to be slightly, but not significantly lower in COPD, whereas surface HLA-DR molecules were significantly reduced (p < 0.005 vs controls). Frequencies of QAP alleles were not different between the COPD patients and controls, but the QBP 5.12 allele was significantly more frequent in COPD than in controls (chi 2 = 10.83, p = 0.0182, RR 5.5). In conclusion, individuals with exacerbated chronic obstructive pulmonary disease have reduced surface DR molecule expression and an increased frequency of the QBP 5.12 allele. The possible relationship between these two features and the possible role of cytokines in reducing human leukocyte antigen-DR expression in exacerbated chronic obstructive pulmonary disease is explored.

Decreased IL-12 production and Th1 cell development by acetyl salicylic acid-mediated inhibition of NF-kappaB

IL-12 is a 75-kDa heterodimeric cytokine composed of two covalently linked p35 and p40 chains. This pro-inflammatory cytokine plays a prominent role in the development of Th1 cell-mediated immune responses. Th1 cell-mediated immune responses have been implicated in the pathogenesis of chronic inflammatory autoimmune diseases. Thus, IL-12 appears to be a critical factor in the generation and maintenance of chronic inflammatory conditions. In this study, we investigated the effects of a commonly prescribed anti-inflammatory drug, acetyl salicylic acid (ASA), on IL-12 production and Th1 cell development. ASA was found to inhibit secretion of the IL-12 heterodimer as well as p40 monomer by human monocytic cells. This was associated with the down-regulation of IL-12p40 mRNA expression. Analysis of the regulation of the p40 gene promoter revealed that ASA inhibited NF-kappaB activation and binding to the p40-kappaB site in the p40 promoter, leading to transcriptional repression of the p40 gene. Addition of ASA to an in vitro T helper cell differentiation system, at concentrations compatible with plasma levels reached during anti-inflammatory therapy, resulted in reduced development of Th1 cells. These results suggest that the inhibition of NF-kappaB activation by ASA leads to down-regulation of IL-12 production and inhibition of Th1 cell development.

Childhood Guillain-Barré syndrome in Paraguay, 1990 to 1991

During 1990 to 1991, through a national surveillance program for poliomyelitis, the Paraguayan Ministry of Health received reports of 50 children with incident acute flaccid paralysis (< 15 years old). On the basis of established criteria, 37 were diagnosed with Guillain-Barré syndrome. The average annual incidence rate for 1990 to 1991 was 1.1/100,000 children. The clinical course was more benign than reported in other pediatric series. There were low rates of hospitalization (57%), respiratory compromise (8%), and intubation (5%). The overall severity, however, was similar to that described in previous reports, with a 3% case-fatality rate and an 81% total recovery rate at 12 months. Seventy-six percent of patients had symptom onset during January to April, the warmest months of the year. Thirty percent of patients had definite or possible exposure to organophosphate pesticides, and the peak use coincides with the peak incidence of Guillain-Barré syndrome. There was no correlation between occurrence of Guillain-Barré syndrome and prior immunization.