Citations

Transforming growth factor β (TGF-β) is critical for the development and maintenance of epithelial structures. Because receptor localization and trafficking affect the cellular and organismal response to TGF-β, the present study was designed to address how such homeostatic control is regulated. To that end, we identify a new role for the mammalian retromer complex in maintaining basolateral plasma membrane expression of the type II TGF-β receptor (TβRII). Retromer and TβRII associate in the presence or absence of TGF-β ligand. After retromer knockdown, although TβRII internalization and trafficking to a Rab5-positive compartment occur as in wild-type cells, receptor recycling is inhibited. This results in TβRII mislocalization from the basolateral to both the basolateral and apical plasma membranes independent of Golgi transit and the Rab11-positive apical recycling endosome. The data support a model in which, after initial basolateral TβRII delivery, steady-state polarized TβRII expression is maintained by retromer/TβRII binding and delivery to the common recycling endosome.

Abstract Altered B cell function is important in the pathogenesis of rheumatoid arthritis (RA). In this report, we show that patients with active RA have an increased frequency of CD32B low/neg cells in the CD27+IgD− memory B cell subset and that these changes are associated with phenotypic and functional B cell activation. Studies using PBMCs from healthy donors revealed that downregulation of CD32B on B cells is mediated by CD40–CD40L interactions and is potentiated by IL-4 and inhibited by both IL-10 and IL-21. These findings appear physiologically relevant because CD4 T cell expression of CD40L correlated with the frequency of CD32B low/neg cells in the CD27+IgD− memory B subset in patients with RA. Our data support a model in which high levels of CD40L, present on circulating T cells in patients with RA, causes B cell activation and CD32B downregulation, resulting in secondary protection of memory B cells from CD32B-mediated cell death.

BackgroundThe AMICUS (Fenwal, Inc.) was cleared in the United States for platelet (PLT) and plasma collection in 1996 with subsequent clearances for the collection of other blood products. Although not previously used for therapeutic plasma exchange (TPE), new disposables, software, and hardware were developed to enable TPE on the AMICUS.Study Design and MethodsA multicenter, randomized, nonblinded, crossover paired treatment protocol was performed. Thirty patients with orders for at least two TPE procedures were randomly assigned to the AMICUS or the COBE Spectra (TerumoBCT) for the first treatment. Each patient was crossed over to the other device using the same procedure settings from the first procedure. The primary objective compared efficiency of plasma removal (EPR) with secondary objectives of comparing PLT and hemoglobin (Hb) waste plasma content, coagulation factor and complement activation, fluid balance tracking accuracy, procedure length, and adverse events.ResultsThe EPR for the AMICUS (81.9 ± 7.62%) was superior to that of the COBE Spectra (75.2 ± 6.29%; p = 0.00001). The AMICUS also demonstrated statistically higher fluid balance accuracy (99.84%) compared to that of the COBE Spectra (98.83%; p < 0.0001) and a statistically shorter procedure time (103.9 ± 30.8 vs. 110.5 ± 27.1 min, p < 0.001). No significant differences with regard to PLT and Hb content in the waste plasma, change in patient PLT count, or changes in markers of coagulation and complement cascade activation were seen. Frequency and severity of adverse reactions were similar.ConclusionThe AMICUS separator can effectively perform TPE. The AMICUS demonstrated superior plasma removal efficiency compared to the COBE Spectra with no evidence of significant differences in PLT removal, hemolysis, and coagulation or complement activation.

Abstract Pneumocystis carinii causes life-threatening pneumonia in immunocompromised patients. The inability to culture P. carinii has hampered basic investigations of the organism's life cycle, limiting the development of new therapies directed against it. Recent investigations indicate that P. carinii is a fungus phylogenetically related to other ascomycetes such as Schizosaccharomyces pombe. The cell cycles of S. pombe and homologous fungi are carefully regulated by cell-division-cycle molecules (cdc), particularly cell-division-cycle 2 (Cdc2), a serine–threonine kinase with essential activity at the G1 restriction point and for entry into mitosis. Antibodies to the proline–serine–threonine–alanine–isoleucine–arginine (PSTAIR) amino-acid sequence conserved in Cdc2 proteins specifically precipitated, from P. carinii extracts, a molecule with kinase activity consistent with a Cdc2-like protein. Cdc2 molecules exhibit differential activity throughout the life cycle of the organisms in which they occur. In accord with this, the P. carinii Cdc2 showed greater specific activity in P. carinii trophic forms (trophozoites) than in spore-case forms (cysts). In addition, complete genomic and complementary DNA (cDNA) sequences of P. carinii Cdc2 were cloned and found to be most closely homologus to the corresponding sequences of other pathogenic fungi. The function of P. carinii cdc2 cDNA was further documented through its ability to complement the DNA of mutant strains of S. pombe with temperature-sensitive deficiencies in Cdc2 activity. The P. carinii cdc2 cDNA restored normal Cdc2 function in these mutant strains of S. pombe, and promoted fungal proliferation. These studies represent the first molecular analysis of the cell-cycle-regulatory machinery in P. carinii. Further understanding of P. carinii's life cycle promises novel insights for preventing and treating the intractable infection it causes in immunocompromised patients.