Quantitative Association Tests of Immune Responses to Antigens of Mycobacterium Tuberculosis: A Study of Twins in West Africa

There is now considerable evidence that host genetic factors are important in determining the outcome of infection with Mycobacterium tuberculosis (MTB). The aim of this study was to assess the role of several candidate genes in the variation observed in the immune responses to MTB antigens. In-vitro assays of T-cell proliferation, an in-vivo intradermal delayed hypersensitivity response; cytokine and antibody secretions to several mycobacterial peptide antigens were assessed in healthy, but exposed, West African twins. Candidate gene polymorphisms were typed in the NRAMP1, Vitamin D receptor, IL10, IL4, IL4 receptor and CTLA-4 genes. Variants of the loci IL10 (-1082 G/A), CTLA-4 (49 A/G) and the IL4 receptor (128 A/G) showed significant associations with immune responses to several antigens. T-cell proliferative responses and antibody responses were reduced, TNF-alpha responses were increased for subjects with the CTLA-4 G allele. The T-cell proliferative responses of subjects with IL10 GA and GG genotypes differed significantly. IL4 receptor AG and GG genotypes also showed significant differences in their T-cell proliferative responses to MTB antigens. These results yield a greater understanding of the genetic mechanisms that underlie the immune responses in tuberculosis and have implications for the design of therapeutic interventions.

Regulatory T-cells infiltrate periodontal disease tissues

CD4(+) CD25(+) regulatory T ( Tr) cells are critical in regulating the immune response and thereby play an important role in the defense against infection and control of autoimmune diseases. Our previous studies demonstrated the involvement of autoimmune responses in periodontitis. The aim of this study was to identify CD4(+) CD25(+) Tr cells in periodontitis tissues and compare them with those in gingivitis tissues. Immunohistological analysis of CD4, CD25, and CTLA- 4 and the gene expression analysis of FOXP3, TGF- beta 1, and IL-10 on gingival biopsies revealed the presence of CD4(+) CD25(+) Tr cells in all tissues. In periodontitis, the percentage of CD4(+) CD25(+) Tr cells increased with increasing proportions of B-cells relative to T- cells. FOXP3, a characteristic marker for CD4(+) CD25(+) Tr cells, TGF- beta 1 and IL-10 were expressed more highly in periodontitis compared with gingivitis. These findings suggest that CD4(+) CD25(+) Tr cells and possibly other regulatory T- cell populations do exist and may play regulatory roles in periodontal diseases.

Timing, magnitude, and location of initial soluble aluminum injuries to mungbean roots

Despite a century's knowledge that soluble aluminum (Al) is associated with acid soils and poor plant growth, it is still uncertain how Al exerts its deleterious effects. Hypotheses include reactions of Al with components of the cell wall, plasmalemma, or cytoplasm of cells close to the root tip, thereby reducing cell expansion and root growth. Digital microscopy was used to determine the initial injuries of soluble Al to mungbean (Vigna radiata L.) roots. Roots of young seedlings were marked with activated carbon particles and grown in 1 mm CaCl2 solution at pH 6 for ca. 100 min (control period), and AlCl3 solution was added to ensure a final concentration of 50 muM Al (pH 4). Further studies were conducted on the effects of pH 4 with and without 50 muM Al. Four distinct, but possibly related, initial detrimental effects of soluble Al were noted. First, there was a 56-75% reduction in the root elongation rate, first evident 18-52 min after the addition of Al, root elongation continuing at a decreased rate for ca. 20 It. Decreasing solution pH from 6 to 4 increased the root elongation rate 4-fold after 5 min, which decreased to close to the original rate after 130 min. The addition of Al during the period of rapid growth at pH 4 reduced the root elongation rate by 71% 14 min after the addition of Al. The activated carbon marks on the roots showed that, during the control period, the zone of maximum root growth occurred at 2,200-5,100 mum from the root tip (i.e. the cell elongation zone). It was there that Al first exerted its detrimental effect and low pH increased root elongation. Second, soluble Al prevented the progress of cells from the transition to the elongation phase, resulting in a considerable reduction of root growth over the longer term. The third type of soluble Al injury occurred after exposure for ca. 4 h to 50 mum Al when a kink developed at 2,370 mum from the root tip. Fourth, ruptures of the root epidermal and cortical cells at 1,900-2,300 mum from the tip occurred greater than or equal to4.3 h after exposure to soluble Al. The timing and location of Al injuries support the contention that Al initially reduces cell elongation, thus decreasing root growth and causing damage to epidermal and cortical cells.

Seasonal patterns of growth, dehydrins and water-soluble carbohydrates in genotypes of Dactylis glomerata varying in summer dormancy

Background and Aims Summer dormancy in perennial grasses has been studied inadequately, despite its potential to enhance plant survival and persistence in Mediterranean areas. The aim of the present work was to characterize summer dormancy and dehydration tolerance in two cultivars of Dactylis glomerata (dormant 'Kasbah', non-dormant 'Oasis') and their hybrid using physiological indicators associated with these traits. Methods Dehydration tolerance was assessed in a glasshouse experiment, while seasonal metabolic changes which produce putative protectants for drought, such as carbohydrates and dehydrins that might be associated with summer dormancy, were analysed in the field. Key Results The genotypes differed in their ability to survive increasing soil water deficit: lethal soil water potential (ψ(s)) was -3(.)4 MPa for 'Kasbah' (although non-dormant), -1(.)3 MPa for 'Oasis', and -1(.)6 MPa for their hybrid. In contrast, lethal water content of apices was similar for all genotypes (approx. 0(.)45 g H2O g d. wt(-1)), and hence the greater survival of 'Kasbah' can be ascribed to better drought avoidance rather than dehydration tolerance. In autumn-sown plants, 'Kasbah' had greatest dormancy, the hybrid was intermediate and 'Oasis' had none. The more dormant the genotype, the lower the metabolic activity during summer, and the earlier the activity declined in spring. Decreased monosaccharide content was an early indicator of dormancy induction. Accumulation of dehydrins did not correlate with stress tolerance, but dehydrin content was a function of the water status of the tissues, irrespective of the soil moisture. A protein of approx. 55 kDa occurred in leaf bases of the most dormant cultivar even in winter. Conclusions Drought avoidance and summer dormancy are correlated but can be independently expressed. These traits are heritable, allowing selection in breeding programmes.