Increasing evidence suggests an important role for cytokines in the regulation of eosinophilic inflammation. In the present study we investigated the distribution of leukocytes, lymphocyte subsets, their activation state, and the cytokine profile present in BAL fluid from patients with various lung diseases associated with eosinophilia. For this purpose, we analyzed the levels of IL-1 beta, IL-2, IL-4, IL-5, IL-6, IL-8, GM-CSF, TNF-alpha, and IFN-gamma, as well as soluble IL-2 and TNF receptors, in concentrated bronchoalveolar lavage (BAL) fluid obtained from clearly defined patients with allergic and nonallergic asthma, eosinophilic pneumonia, allergic bronchopulmonary aspergillosis (ABPA), hypersensitivity pneumonitis, and idiopathic pulmonary fibrosis. BAL fluid from normal individuals and sarcoidosis patients was analyzed as noneosinophilic controls. BAL cytokine levels were compared with the cellular infiltrate and the activation state of CD4+ and CD8+ T cells as measured by the expression of IL-2 receptors (CD25), HLA-DR, and the very late activation antigen VLA-1. Beside the characteristic leukocyte infiltrate in the various lung diseases, all patients demonstrated significantly increased numbers of activated CD4 and CD8 T cells compared with normal individuals. The analysis of the cytokine profile present in BAL fluid revealed a T helper type 2 (Th2) cell cytokine pattern, with elevated IL-4 and IL-5 but normal levels of IL-2 or IFN-gamma in allergic asthma. ABPA patients demonstrated significantly increased levels of IL-4 and IL-5, with low but significantly elevated concentrations of IL-2 and IFN-gamma. In contrast, the analysis of the cytokine profile in sarcoidosis patients revealed a Th1 cell cytokine pattern characterized by increased concentrations of IL-2 and IFN-gamma but normal levels of IL-4 or IL-5. All other patient groups showed a cytokine pattern incompatible with a pure Th1 or Th2 cell response, because IL-5, IL-2, and IFN-gamma were found to be significantly increased. The BAL fluid analysis of the other, mainly non-T cell-derived cytokines and soluble receptors showed increased levels in all patients compared with normal individuals and may represent the ongoing inflammatory responses. In conclusion, whereas increased IL-4 levels were found only in diseases characterized by increased IgE production, IL-5 was elevated in all patients with increased numbers of eosinophils. The close correlation between IL-5 levels, number of eosinophils, and activated T cells further supports a role for IL-5 in causing tissue eosinophilia.

African trypanosomes that cycle between mammalian hosts and the tsetse fly vector must be poised to survive in different environments. The control of stage-specific gene expression is undoubtedly one of the keys to successful adaptation, but no regulatory elements have been defined to date. Procyclins (also known as procydic acidic repetitive proteins) are specifically expressed on the surface of procyclic and epimastigote forms in the fly. Procyclin genes are already transcribed in bloodstream forms, but stable mRNA, and later the protein, are first detected when the parasites begin to differentiate into procydic forms. We have now identified a region of 16 bases that forms part of a predicted stem-oop structure in the 3' untranslated regions of different procyclin mRNAs; both the sequence and the secondary structure of this 16-mer appear to be required for efficient translation of a reporter gene in procycic forms. The level of steady-state mRNA, its polyadenylylation, and its distribution in the cell are all unaffected by the presence or absence of this element. Deletion of the 16-mer alone reduces expression more than removal or reversal of the entire 3' untranslated region and flanking region, suggesting that there are additional negative regulatory elements in the same 3' untranslated region.

The procyclin-associated genes (PAGs) of Trypanosoma brucei are located downstream of tandemly repeated procyclin genes and belong to the same alpha-amanitin-resistant polycistronic transcription units. In procyclic form trypanosomes the PAG 1 pre-mRNA is alternatively spliced to give rise to three transcripts of 2.7 kb, 1.8 kb and 1.3 kb. The two larger transcripts contain additional short open reading frames (ORFs) upstream of the major ORF. Trans-splicing to generate these transcripts occurs downstream of three different polypyrimidine tracts. A minor population of procyclin mRNAs is also generated by alternative splicing at a polypyrimidine tract that begins 524 bp upstream of the major splice acceptor site of the procyclin beta-gene. The same polypyrimidine tract is also required for accurate polyadenylation of mRNAs from the upstream procyclin alpha-gene (1). Alternatively polyadenylated forms of PAG 1 mRNAs can also be detected. All polyadenylation sites are found at a similar distance upstream of splice-acceptor sites, in each case with a polypyrimidine tract between them. Our results point to a dual role for polypyrimidine tracts in the maturation of trypanosome mRNAs.

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