Faculty Bibliography

BACKGROUND:Ibuprofen is a cyclooxygenase inhibitor that is effective in treating patent ductus arteriosus in preterm infants. However, recent trials have suggested that it may increase the risk of developing necrotizing enterocolitis and chronic lung disease. Apoptosis of neutrophils is impaired in newborns, leading to reduced clearance of activated cells and possibly contributing to the susceptibility of infants to these inflammatory diseases. OBJECTIVES/OBJECTIVE:In the present studies, we investigated the hypothesis that ibuprofen reduces neonatal neutrophil apoptosis in the setting of hypoxia or lipopolysaccharide (LPS). METHODS:Neutrophils and peripheral blood mononuclear cells were isolated from adult and cord blood and cultured in the presence or absence of ibuprofen (1.5 mM), hypoxia (<5% O2), and bacterial LPS (100 ng/ml). Apoptosis was quantified by measuring binding of FITC-Annexin V using flow cytometry. Cytokine concentrations in cell supernatants were measured by ELISA. RESULTS:After 24 h, 20% of adult and 14% of neonatal neutrophils were apoptotic. Apoptosis was reduced by hypoxia in both adult and neonatal cells. Ibuprofen further reduced neutrophil apoptosis, but only when the cells were cultured in the presence of mixed leukocytes. This suggests that the effects of ibuprofen on apoptosis are dependent on soluble products secreted by peripheral blood mononuclear cells. We found that production of tumor necrosis factor (TNF)-alpha by neonatal leukocytes was significantly increased by ibuprofen, and was further increased following exposure to ibuprofen in the presence of LPS and hypoxia. In contrast, production of macrophage inflammatory protein (MIP)-1alpha was not affected by treatment with ibuprofen, and ibuprofen blocked induction of this chemokine by LPS. CONCLUSION/CONCLUSIONS:We conclude that the net effect of ibuprofen on neutrophils is antiapoptotic, especially in the presence of hypoxia or LPS. This effect may be mediated, in part, by increased production of TNF-alpha by peripheral blood mononuclear cells. These data suggest that treatment of infants with ibuprofen, in the presence of infection and/or tissue hypoperfusion/hypoxia, may contribute to the development of inflammatory diseases.

PROBLEM/OBJECTIVE:To determine if first trimester missed abortion decidua is characterized by an altered immune cell profile and/or a modified interleukin (IL)-10 and interferon (IFN)-gamma production pattern compared with decidua from elective termination. METHOD OF STUDY/METHODS:Flow cytometry and immunohistochemistry techniques were used to determine the decidual immune cell phenotypic profile and production pattern of IL-10 and IFN-gamma in cases of elective termination (n = 14) and missed abortion (n = 12). RESULTS:Both groups had a similar proportion of CD56+ CD16-, CD56+ CD16+, CD19+, CD3+, CD4+, CD8+, alphabeta T cells and gammadelta T cells. The majority of alphabeta and gammadelta positive T cells in both groups coexpressed the natural killer (NK) cell marker CD56, but lacked cell surface expression of CD3. Diminished decidual IL-10 staining was noted in 7/10 missed abortion cases compared with none of the elective termination cases (n = 12) (P = 0.007). A uniform decidual IFN-gamma staining pattern was observed in both groups. CONCLUSION/CONCLUSIONS:Decreased IL-10 production coupled with a sustained IFN-gamma presence noted in missed abortion compared with elective termination cases suggest that these cytokines may be important determinants in pregnancy outcome. In contrast, differences in the proportion of immune cells between both groups may not be a critical factor in early pregnancy loss. In normal pregnancy, decidual alphabeta and gammadelta positive T cells with reduced CD3 on their cell surface may be intrinsically restricted in T-cell receptor (TCR)-mediated activation.

Recent studies have defined several phenotypic and molecular changes associated with the maturation of naive human B cells within the milieu of germinal centers. Although naive B cells serve as natural precursors to germinal center (GC)/memory (M) subpopulations, little is known about the physiological requirements for the survival of the naive B cell pool in the absence of cell-cell contact or Ag-mediated activation. Because IL-4 induces expression of several membrane receptors such as CD23 which are uniquely present on resting human naive B lymphocytes, we hypothesized that these cells might be intrinsically programmed to respond to IL-4 in the absence of cell division. Using buoyant density-dependent isolation and further enrichment by negative/positive selection of human naive and GC/M subpopulations, we characterized cytokine receptor moieties on these cells and analyzed their survival and growth in the presence of IL-4 or IL-10. Resting naive B cells expressed significantly higher IL-4 receptor alpha-chain on their cell surface than the combined GC/M subpopulation. The IL-10 receptor and the IL-2 receptor gammac chain were almost equally expressed on both subpopulations. When cultured in vitro, the addition of IL-4, but not IL-10, protected naive B cells from apoptosis in the absence of activation and growth. However, IL-4 exerted no such effect on resting GC/M B cells. These data support the hypothesis that IL-4 plays a pivotal role in the survival and maintenance of resting human naive B cells.

Control of antifetal immune responses is thought to be regulated locally by the placenta. Because the physiologic programming of the placenta across gestation is likely to influence the local immunity, we hypothesize that a potent anti-inflammatory cytokine such as IL-10 may be produced in a gestational age-dependent manner. In the present study, we examined the expression of IL-10 and its receptor in placental explants or freshly isolated cytotrophoblasts from different gestational ages and compared it with the expression profiles of other cytokines. First and second trimester placental tissues from normal pregnancies predominantly expressed IL-10, whereas the levels of IL-2, IL-4, and IFN-gamma were mostly below detection throughout pregnancy. The expression of IL-10, but not its receptor, diminished significantly in term placental tissues collected "before" the onset of labor and did not change appreciably "after" labor. On the other hand, TNF-alpha and IL-1beta were significantly up-regulated in response to labor-associated conditions. IL-10 expression was transcriptionally attenuated at term as observed in cytotrophoblasts. In contrast to the placental cytokine milieu, autologous PBMCs, when activated with PHA, secreted significant amounts of IL-2, IL-4, IL-10, and IFN-gamma, albeit with a statistically significantly enhanced IL-10 production in first trimester compared with age-matched nonpregnant women. These data suggest that IL-10 is expressed in the placenta in a gestational age-dependent manner and that its down-regulation at term may be an important mechanism underlying the subtle changes associated with parturition.

Fas ligand (FasL)-dependent apoptosis has been implicated in the control of tissue-damaging inflammatory responses in several immune privileged sites. Here, we present data demonstrating that FasL is expressed on human trophoblast cells throughout pregnancy and transduces growth inhibitory/death signals in cells bearing its receptor, Fas (CD95). Immunohistochemical analysis detected FasL-positive staining in the trophoblast layer of villi of first- and second-trimester and term (no labor) placental tissues, as well as in freshly isolated cytotrophoblasts representing these gestational ages. In contrast, term placental tissues and cytotrophoblasts from labor-associated deliveries exhibited significantly reduced FasL expression, suggesting that parturition altered the characteristics of trophoblast cells. FasL-specific immunoblotting of cytotrophoblast cell lysates further confirmed these results. To assess the functionality of FasL expressed on cytotrophoblasts, we co-cultured these cells with Fas-bearing Jurkat T cells. Cytotrophoblasts from early pregnancy, or term with no labor, significantly inhibited growth in Jurkat cells, evident even at a 1:1 effector:target cell ratio, as determined by the incorporation of [3H]thymidine. Similar results were obtained when a FasL-positive colon carcinoma cell line, SW620, was used in place of cytotrophoblasts. In contrast, term cytotrophoblasts from labor deliveries exhibited poor FasL expression and were quantitatively much less proficient in inhibiting [3H]thymidine incorporation in Jurkat cells. These data indicate that FasL could participate in modulating the inflammatory responses associated with labor and suggest intrinsic molecular differences in the placental microenvironment before and after labor .

The functional differences between IgDhighCD38- naive and IgD-CD38- memory (M) or IgDlowCD38+ germinal center (GC) B cells may stem from their variable response to signals that regulate activation, proliferation, and differentiation. In this report, we provide evidence for differential induction of cell cycle regulators in tonsillar human B cell subpopulations that were activated with anti-IgM and anti-CD40 in the presence or absence of IL-2, IL-4, or IL-10. Naive (IgDhigh) B cells exhibited a significant proliferative response to IL-4, but not to IL-2 or IL-10, whereas these cytokines triggered variable levels of growth in the combined GC/M subpopulation (referred to as IgDlow), as measured by [3H]thymidine incorporation. Induction of growth by cytokines in B cell subpopulations strictly correlated with the increased levels of cyclin D3 and cyclin-dependent protein kinase (cdk) 6. Moreover, only cyclin D3/cdk6 complexes were functional as observed in both naive and GC/M B cells stimulated in the presence of IL-4. In addition, active growth was associated with cytokine-mediated elimination of the cell cycle inhibitor p27. The significance of p27 in human B cell cycle was further demonstrated by rapamycin-mediated growth inhibition of IL-4-dependent proliferation, which resulted in strikingly increased p27 levels. Taken together, our findings suggest that cyclin D3, cdk6, and p27 play key roles in IL-2-, IL-4-, and IL-10-mediated human B cell proliferation. Furthermore, these results may provide a molecular basis for different cycling characteristics of naive and GC/M B cell subpopulations.