Altitudinal gradient drives regional and local diversity and composition patterns of epiphyllous bryophytes in ecological refuges

'Brejos de altitude' is an ecosystem that has been subjected to severe exploitation, leading to an intense reduction in Brazil. Understanding the patterns of bryophyte diversity and composition, particularly of specialized species such as the epiphylls, to anthropic and abiotic variables is crucial for implementing protection measures. We investigated the relationship between composition and diversity of epiphyllous bryophytes and anthropic (edge effects) and abiotic (altitude) variables at local (within each 'Brejo') and regional (set of three 'Brejos') scale. Abiotic and anthropic variables were correlated with alpha and beta diversity (decomposed into species replacement and richness differences) using GLM. Their effects on species composition were evaluated using PERMANOVA. The localities at higher elevations harboured a richer bryoflora and overall beta diversity patterns were associated with altitude and locality, which acted over different scales. Regionally, the contribution of richness differences was limited with increasing altitude. Yet, dissimilarities among localities were associated with richness differences and replacement, denoting the importance of local factors. The composition was explained by local factors interacting with the regional altitudinal gradient. Anthropic activity was significant only when interacting with local factors and altitudinal gradient. Environmental filtering associated with altitude played a more important role in shaping the diversity and composition of epiphyllous bryophytes, at both regional and local scales. Each 'Brejo' acts as an ecological refuge, harbouring part of the whole environmental gradient, and presents a unique floristic composition. Moreover, partitioning beta diversity highlighted the interplay of local and regional forces shaping diversity patterns.

IFN-beta and TGF-beta differentially regulate IL-12 activity in human peripheral blood mononuclear cells

Both IFN-beta and TGF-beta have demonstrated their ability to antagonize several of the stimulatory activities of IFN-gamma on human macrophages, thereby classifying them as Th2-like. Aiming at a further characterization of their role in Th1/Th2 development, we studied their possible interaction with IL-12, the key Th1 cytokine. We found that IFN-beta by itself induced modest amounts of IFN-gamma, but was able to synergize with IL-12 for IFN-gamma induction. TGF-beta, on the other hand, had no effect by itself and inhibited significantly the IL-12-induced IFN-gamma secretion. The differential effect of IFN-beta and TGF-b on IL-12 bioactivity was most pronounced upon IFN-gamma synthesis, since IFN-beta induced only marginal amounts of IL-10 and IL-12 and TGF-beta diminished constitutive IL-10 production, while neither had a significant effect on TNF-alpha production. Although monocytes did not produce detectable IFN-gamma with any of the stimuli, adherent cells were found to cooperate with non-adherent lymphocytes for maximal IFN-gamma production. However, IL-18, a monocyte-derived IFN-gamma-inducing cytokine able to synergize with IL-12, was undetectable in IFN-beta or IFN-beta+IL-12-stimulated cells. In conclusion, the ability of IFN-beta to synergize with IL-12 for IFN-gamma synthesis, without significant concomitant IL-10 production, suggest a strong boost to Th1 development, which seems to be IL-18-independent.