P-glycoprotein functions as a differentiation switch in antigen presenting cell maturation.

P-glycoprotein (P-gp) expressed on human antigen presenting cells (APC) regulates alloantigen-dependent T-cell activation, but the associated mechanisms are not well understood. Here we demonstrate that P-gp functions in IL-12-dependent monocyte differentiation into dendritic cell (DC) lineages during APC maturation, thereby regulating the capacity of myeloid-derived APCs to elicit alloimmune Th1 responses. Human CD14+ monocytes cultured in vitro in the presence of IL-4/GM-CSF differentiated into CD14(-) CD1A+ APCs of the immature DC phenotype. In contrast, P-gp blockade during differentiation inhibited CD1a induction, down-regulated CD80 expression, enhanced CD86 expression and induced CD68 expression. APCs differentiated in the presence of P-gp blockade stimulated alloimmune T-cell proliferation significantly less than controls and this effect was associated with 97% inhibition of Th1 IFN-gamma production, but preserved Th2 IL-5 secretion. MAb-mediated blockade of the P-gp transport substrate IL-12 in the course of APC differentiation also inhibited IFN-gamma production, while addition of rIL-12 to P-gp-blocked APC differentiation cultures significantly reversed this effect, demonstrating that P-gp functions in APC differentiation in part via IL-12 regulation. Our findings define a novel role for P-gp as a differentiation switch in APC maturation and resultant alloimmune Th1 responses, thereby identifying P-gp as a potential novel therapeutic target in allotransplantation.

P-glycoprotein--a novel therapeutic target for immunomodulation in clinical transplantation and autoimmunity?

P-glycoprotein, the human MDR1 gene product and cancer multidrug resistance-associated ATP-binding cassette transporter, is physiologically expressed on peripheral blood mononuclear cells, but its role in cellular immunity is only beginning to be elucidated. A role of P-glycoprotein in the secretion of several T cell- and antigen presenting cell-derived cytokines has been described, and additional functions of the molecule have been identified in lymphocyte survival and antigen presenting cell differentiation. Taken together, these findings provide compelling evidence that P-glycoprotein serves several distinct functions in the initiation of primary immune responses, and a critical role of the molecule in functional immune responses is now established. Here, we will review the current understanding of P-glycoprotein function in T cell activation and antigen presenting cell function, which are relevant to the fields of clinical transplantation and autoimmunity, and summarize the evidence for in vitro and in vivo immunomodulatory actions of several known P-glycoprotein-inhibiting agents currently in clinical use for other indications. We suggest that it is the P-glycoprotein-inhibitory function of many of these agents that underly their immunoregulatory capacities. Thus, the established immunoregulatory function of P-glycoprotein and the availability of P-glycoprotein-inhibitory drugs raise the possibility that P-glycoprotein may represent a promising novel therapeutic target for immune modulation in acute and chronic allograft rejection, and cell-mediated autoimmune disorders.

Fibrinogen and factor VII levels improve with glycemic control in patients with type 1 diabetes mellitus who have microvascular complications.

To determine whether the hypercoagulable state of patients with complications of diabetes can be reversed toward normal, a group of insulin-dependent individuals with proteinuria was treated with intensive insulin protocols. A statistically significant (P<.001) improvement in control of diabetes was achieved (mean +/- SEM glycosylated hemoglobin, 9.51% +/- 0.35% at baseline to 8.36% +/- 0. 39% at 12 months; and mean +/- SEM advanced glycosylated end products, 14.8 +/- 2.8 U/mL at baseline to 8.4 +/- 1.5 U/mL at 12 months). There were statistically significant decreases in 2 procoagulant factors: mean +/- SEM baseline elevated plasma factor VII, 128.69% +/- 5.63% at baseline to 106.24% +/- 3.43% at 12 months (P =.002); and mean +/- SEM plasma fibrinogen, 12.3 +/- 0.7 micromol/L (417.3 +/- 24.7 mg/dL) at baseline to 10.2 +/- 0.7 micromol/L (348.8 +/- 22.6 mg/dL) at 12 months (P =.04). Throughout the study, lipid fractions did not change significantly. Because plasma factor VII and fibrinogen concentrations were elevated while cholesterol and triglyceride concentrations were not, more attention should be paid to procoagulants as markers for thromboembolic complications in diabetic patients undergoing intensive insulin therapy.

Recruitment and the role of nuclear localization in polyglutamine-mediated aggregation.

The inherited neurodegenerative diseases caused by an expanded glutamine repeat share the pathologic feature of intranuclear aggregates or inclusions (NI). Here in cell-based studies of the spinocerebellar ataxia type-3 disease protein, ataxin-3, we address two issues central to aggregation: the role of polyglutamine in recruiting proteins into NI and the role of nuclear localization in promoting aggregation. We demonstrate that full-length ataxin-3 is readily recruited from the cytoplasm into NI seeded either by a pathologic ataxin-3 fragment or by a second unrelated glutamine-repeat disease protein, ataxin-1. Experiments with green fluorescence protein/polyglutamine fusion proteins show that a glutamine repeat is sufficient to recruit an otherwise irrelevant protein into NI, and studies of human disease tissue and a Drosophila transgenic model provide evidence that specific glutamine-repeat-containing proteins, including TATA-binding protein and Eyes Absent protein, are recruited into NI in vivo. Finally, we show that nuclear localization promotes aggregation: an ataxin-3 fragment containing a nonpathologic repeat of 27 glutamines forms inclusions only when targeted to the nucleus. Our findings establish the importance of the polyglutamine domain in mediating recruitment and suggest that pathogenesis may be linked in part to the sequestering of glutamine-containing cellular proteins. In addition, we demonstrate that the nuclear environment may be critical for seeding polyglutamine aggregates.

Frequent loss of heterozygosity at the TEL gene locus in acute lymphoblastic leukemia of childhood.

TEL is a new member of the ETS family of transcription factors which is rearranged in a number of hematologic malignancies with translocations involving chromosome band 12p13. In some cases, both TEL alleles are affected, resulting in loss of wild-type TEL function in the leukemic cells. In addition, 5% of children with acute lymphoblastic leukemia (ALL) have 12p12-p13 deletions, suggesting that a tumor suppressor gene resides on 12p. These observations led us to consider whether TEL loss of function may contribute to the pathogenesis of ALL. In this report we show that the TEL gene maps between the polymorphic markers D12S89 and D12S98, and we use these flanking markers to screen paired diagnosis and remission samples from 81 children with ALL for loss of heterozygosity (LOH) at the TEL gene locus. Fifteen percent of informative patients showed TEL LOH which was not evident on cytogenetic analysis. Detailed examination of patients with LOH at this locus showed that the critically deleted region included two candidate tumor suppressor genes: TEL and KIP1, the gene encoding the cyclin-dependent kinase inhibitor p27. These studies show that LOH at the TEL locus is a frequent finding in childhood ALL.

Perception: an experiment to compare "here and now" and "there and then" perspectives.

A basic tenet of humanistic psychology is that "here and now" perception is different from and superior to "there and then" perception. This article describes an experimental test of this tenet. The test is based on the close relationship between categorizing and perceiving of stimuli. Data showed that people tend to use fewer categories to sort stimuli when in a "there and then" perspective than in a "here and now" perspective. This outcome is consistent with a theorem of information theory regarding signal to noise ratio and optimal number of categories.

Hemispheric asymmetry in making absolute judgments of monaurally presented pure tones.

Some recent studies have suggested that hemispheric asymmetry may be related to the quantity of information contained in a stimulus. To test this possibility, 20 subjects were given an auditory absolute-judgment task in which they were required to identify 3, 5, or 7 pure tones recorded on a tape. The presentation was monaural, and headphone placement was randomly alternated across subjects. The left ear showed a statistically significant advantage tones. The result is discussed in terms of previous work on auditory channel-capacity and the desirability of using an absolute-judgment paradigm to study hemispheric asymmetry for other kinds of stimuli is indicated.