Interleukin-10 inhibits IgE-mediated nitric oxide synthase induction and cytokine synthesis in normal human keratinocytes

Human keratinocytes (HK) generate nitric oxide (NO) and proinflammatory mediators following activation with either IgE/anti-IgE immune complexes or a combination of lipopolysaccharide (LPS) and interferon-γ (IFN-γ). Recently, interleukin-10 (IL-10) has been shown to down-regulate various inflammatory responses and to be secreted by lymphocytes and dendritic cells during skin inflammatory reactions. We show here that IL-10 down-regulates the production of tumor necrosis factor (TNF)-α and IL-6 by activated HK. Also, induction of inducible nitric oxide synthase (iNOS) expression in HK by IgE/anti-IgE or LPS/IFN-γ is significantly reduced by the addition of IL-10. This effect is dose dependent and correlates with reduction of iNOS mRNA production and enzyme level. Therefore, IL-10 down-regulates NO-mediated HK inflammatory responses and may thus participate in the regulation of the skin immune network.     

Biochemical and functional alterations induced by CD23 ligation in the human promonocytic cell line U937.

The early events triggered in interleukin-4 (IL-4)-stimulated U937 cells by ligation of CD23/Fc epsilon RII with specific monoclonal antibodies (mAb) were analysed, as a model of the action of this molecule on the differentiation of promonocytic cells. As well as IL-4-activated human monocytes, addition of anti-CD23 mAb to IL-4-treated U937 cells triggered cAMP accumulation but did not evoke significant polyphosphoinositide hydrolysis. However, by a microspectrofluorometric technique allowing single cell analysis, anti-CD23 mAb was found to elicit calcium mobilization in these cells. In addition, the treatment induced phenotypic alterations in these cells, as evidenced by the acquisition of the monocyte marker CD14 and the increase of the alpha-chain (CD11a) and of the common beta-chain (CD18) of the leucocyte function-associated antigen 1 (LFA-1) family antigens. Although weaker than in monocytes, CD23 ligation evoked a small secretion of the pro-inflammatory mediators IL-6 and thromboxane B2. These data suggest that a significant maturation of promonocytic cells towards a more mature monocytic phenotype can be achieved through successive exposure to IL-4 and CD23 ligation.     

Involvement of cAMP in CD3 T cell receptor complex- and CD2-mediated apoptosis of human thymocytes

During intrathymic T cell development, elimination of autoreactive T cell clones by programmed cell death (PCD or apoptosis) is an essential mechanism for self tolerance. The precise intracellular second messengers that lead to this process remain to be determined. In the present work, we show that treatment of freshly isolated thymocytes with an antagonist of the cAMP pathway, the Rp-cAMP, significantly decreases spontaneous death by apoptosis of human thymocytes in vitro. Addition of Rp-cAMP also rescues thymocytes from activation-induced apoptosis following the ligation of surface CD3/T cell receptor complex or CD2 antigens. A cAMP analog, the dibutyryl(Dibut)-cAMP increases PCD of human thymocytes in a dose-dependent manner. Growth and rescue from PCD of thymocytes in the presence of interleukin (IL)-2 or IL-4 are also enhanced by Rp-cAMP and inhibited by Dibut-cAMP. Finally, we detect substantial levels of intracellular cAMP in freshly isolated thymocytes. This study reveals the involvement of cAMP as a second messenger during the apoptosis of normal human thymocytes.     

Origin of malignant centrofacial granulomas: surface markers and gene rearrangement of malignant cells

Malignant centrofacial granuloma (MCFG) is a clinical entity characterized by a relentless ulceration of the upper airway involving the nose, palate, and face, without any demonstrable etiology. The origin of 11 cases were analyzed with the help of cell-surface immunostaining in all and with T-cell receptor gene (TCR) rearrangement in 3. The results show that most of the cases of MCFG are in fact T-cell lymphomas with cell-surface antigens (CD2, CD7, CD3) consistent with either early or mature T lymphocytes. However, some cases exhibit B-lymphoid (CD19, CD20) or histiomonocytic (CD13, CD14) lineage-specific markers. In conclusion, despite its remarkable clinical unity, MCFG is a heterogeneous group of neoplastic diseases, most but not all of which may be classified as T-cell lymphoma.     

Early human thymocyte proliferation is regulated by an externally controlled autocrine transforming growth factor-beta 1 mechanism

Early thymocytes undergo extensive proliferation after their entry into the thymus, but cellular interactions and cytokines regulating this intrathymic step remain to be determined. We analyzed the effects of various T-cell growth factors and cellular interactions on in vitro proliferation of early CD2+CD3/TCR-CD4-CD8- (triple negative [TN]) human thymocytes. Freshly isolated TN cells were then assayed for their growth capacity after incubation with CD2I+III-monoclonal antibody (MoAb), recombinant human interleukin-2 (IL-2), IL-7, and/or IL-4. These cells displayed significant proliferative responses with IL-4, IL- 7, or CD2-MoAb+IL-2. The addition of recombinant transforming growth factor beta (TGF beta) or autologous irradiated CD3+CD8+CD4- cells to TN cell cultures dramatically decreased their growth responses to IL-2 and IL-7, whereas IL-4-induced proliferation was less sensitive to growth inhibition. We thus asked whether the CD8+ cell-derived inhibitory effect was due to TGF beta. The addition of neutralizing anti-TGF beta MoAb completely abolished CD8+ cell-derived inhibition of TN cell growth. Analysis of CD8+ cell-derived supernatants indicated that these cells had low TGF beta 1 production capacity, whereas TN cells secrete significantly high levels of TGF beta 1. Cell fixation studies showed that TN cells were the source of the TGF beta. TGF beta 1 released from TN cells was in the latent form that became the active inhibitory form through interaction of TN cells with CD8+ cells. Together, these data suggest a role for TGF beta 1 as an externally controlled, autocrine inhibitory factor for human early thymocytes, with a regulatory role in thymic T-cell output.     

Development and evaluation of buccoadhesive propranolol hydrochloride tablet formulations: effect of fillers

The buccal mucosa has been investigated for local and systemic delivery of therapeutic peptides and other drugs that are subjected to first-pass metabolism or are unstable within the rest of the gastrointestinal tract. Propranolol hydrochloride (propranolol HCl) is subjected to first-pass effect, therefore formulation of buccal-adhesive dosage form can circumvent this effect. The effect of lactose (a soluble excipient) and dicalcium phosphate (DCP) (an insoluble excipient) on dissolution rate, kinetic of release and adhesion force of buccal-adhesive tablets of propranolol HCl were evaluated. Each tablet composed of 80 mg propranolol HCl, 80 mg hydroxypropylmethylcellulose (HPMC) K4M, polycarbophil AA1 and lactose or DCP with different ratios. The results showed that the presence of the fillers increased dissolution rate of the drug. The release data also showed that the effect of lactose on the dissolution rate was greater than the DCP. Kinetic release of propranolol HCl from buccal-adhesive matrices was affected by the different ratios of polymers and fillers. The fillers reduced the bioadhesion force and this effect was more considerable in formulation containing DCP. In order to determine the mode of release, the data were analyzed based on the equation Q =kt(n). The results showed that an increase in the concentration of HPMC K4M resulted in a reduction in the value of n. The value of n was not significantly affected by an increase in the concentration of lactose or DCP. The values of n in this study were calculated to be between 0.461 and 0.619, indicating both diffusional release and erosional mechanism.     

In vitro effects of sodium diethyldithiocarbamate (Imuthiol) on human T lymphocytes

The effect of purified diethyldithiocarbamate, DTC (Imuthiol) on human T-cell dependent functions has been investigated. The mitogenic response of PHA-stimulated peripheral blood lymphocytes (PBL) was significantly enhanced by Imuthiol at low drug concentration (10(-7) mg/ml). The same dose of Imuthiol also stimulated IL2 production by human PBL. This enhancement depended on the presence of adherent cells. These results could, in part, explained the immunostimulant activity of Imuthiol.     

Soluble CD23 (Fc epsilon RII) and interleukin 1 synergistically induce early human thymocyte maturation

The ability of human thymus-derived CD7+CD2-CD3- cells to acquire mature T cell antigens was assessed. Purified CD7+ thymocytes were incubated with rIL-1, rIL-2, and/or recombinant soluble CD23 (rsCD23). Short-term incubation of these cells with only rsCD23 + rIL-1 induced mature T cell antigen expression on at least half of the cells. The induction of CD2 was functionally significant, as these cells became able to respond to CD2 triggering and could proliferate in response to IL-2. Possible sources of CD23 in the thymus are under investigation.     

Isolation of an early T-cell precursor (CFU-TL) from human bone marrow.

CD2-CD3-CD4-CD8- human bone marrow (BM) cells were previously shown to generate T-cell clones in vitro. This capacity was abolished after treatment of this population with anti-CD7 monoclonal antibody and complement. In this study, using rosetting with sheep erythrocytes, complement-dependent cytotoxicity, and specific immunoadherence method, we isolated a minor BM subset that contained more than 80% CD7+CD2-CD3-CD4-CD8- cells with small lymphoid cell morphology. They comprised most early T-cell precursors (CFU-TL) as they displayed high capacity to generate T-cell clones when cultured in limiting dilutions. CFU-TL nature of these cells was also confirmed by the sequential expression of mature T-cell specific markers on their surface after in vitro induction. This BM subset also contained 2% to 3% CFU-GM precursors. Together, these results pointed to the existence of BM CD7+CD2- precursors with high differentiation potential and showed the commitment of most of them to T-cell lineage.     

Quercetin induces apoptosis of Trypanosoma brucei gambiense and decreases the proinflammatory response of human macrophages

In addition to parasite spread, the severity of disease observed in cases of human African trypanosomiasis (HAT), or sleeping sickness, is associated with increased levels of inflammatory mediators, including tumor necrosis factor (TNF)-alpha and nitric oxide derivatives. In the present study, quercetin (3,3',4',5,7-pentahydroxyflavone), a potent immunomodulating flavonoid, was shown to directly induce the death of Trypanosoma brucei gambiense, the causative agent of HAT, without affecting normal human cell viability. Quercetin directly promoted T. b. gambiense death by apoptosis as shown by Annexin V binding. In addition to microbicidal activity, quercetin induced dose-dependent decreases in the levels of TNF-alpha and nitric oxide produced by activated human macrophages. These results highlight the potential use of quercetin as an antimicrobial and anti-inflammatory agent for the treatment of African trypanomiasis.