The enemy within: keeping self-reactive T cells at bay in the periphery

The remarkable capacity of the mammalian immune system to coordinate deadly attacks against numerous invading pathogens, yet turn a blind eye to self-tissues continues to fascinate immunologists. It has been clear for some time that immune cells capable of recognizing self-proteins exist in normal individuals without seemingly causing harm. The 'peripheral tolerance' mechanisms that keep these cells in check are the focus of intense research, not least because defects in these pathways might cause autoimmune diseases. In this review, new developments in our understanding of peripheral tolerance are discussed.     

Differential activation of p53 by the various adducts of mitomycin C

Mitomycin C (MC) is a cytotoxic chemotherapeutic agent that causes DNA damage in the form of DNA cross-links as well as a variety of DNA monoadducts and is known to induce p53. The various DNA adducts formed upon treatment of mouse mammary tumor cells with MC as well as 10-decarbamoyl MC (DMC) and 2,7-diaminomitosene (2,7-DAM), the major MC metabolite, have been elucidated. The cytotoxicity of DMC parallels closely that of MC in a number of rodent cell lines tested, whereas 2,7-DAM is relatively noncytotoxic. In this study, we investigate the ability of MC, DMC, and 2,7-DAM to activate p53 at equidose concentrations by treating tissue culture cell lines with the three mitomycins. Whereas MC and DMC induced p53 protein levels and increased the levels of p21 and Gadd45 mRNA, 2,7-DAM did not. Furthermore, MC and DMC, but not 2,7-DAM, were able to induce apoptosis efficiently in ML-1 cells. Therefore the 2,7-DAM monoadducts were unable to activate the p53 pathway. Interestingly, DMC was able to initiate apoptosis via a p53-independent pathway whereas MC was not. This is the first finding that adducts of a multiadduct type DNA-damaging agent are differentially recognized by DNA damage sensor pathways.     

Plants used by andaman aborigines in gathering rock-bee honey

Economic Botany - The giant rock bee,Apis dorsata, of Asia is a migratory and ferocious wild bee, which has not yet been tamed. It is the chief source of honey and beeswax in the Andaman region...     

Stereoselective synthesis and antifungal activity of (Z)-trans-3-azolyl-2-methylchromanone oxime ethers

A series of (Z)-trans-3-azolyl-2-methylchromanone oxime ethers were stereoselectively synthesized and tested for in vitro antifungal activity. Many of these derivatives exhibit high activity against Candida albicans, Saccharomyces cerevisiae, Aspergillus niger, and Microsporum gypseum.     

Cytokine production by peripheral blood mononuclear cells in recurrent miscarriage

It has been postulated that a proportion of recurrent miscarriage (RM) might be due to immune causes. The objective was to determine whether cytokine expression in peripheral blood mononuclear cell is altered in patients with a history of RM. We compared the levels of IL-2, IL-4, IL-10, IL-13, TGFbeta1 and IFNgamma in the supernatant of Phytohemagglutinin stimulated mononuclear cells in 21 women with RM at the time of 3rd or higher abortion (group I), 32 women who were at least 3 months past their 3rd or higher abortion (group II) and 32 pregnant women with no history of abortion (group III). Gestational age was matched between groups I and III. Group I had higher level of IL-2 than group III (P=0.001). Group II showed higher level of IL-2 (P=0.001) and IFNgamma (P=0.015) than group III. The production of IL-10 by mononuclear cells of group III was higher than both group I (P=0.002) and group II (P=0.001). There was no difference in the levels of IL-2, IL-10 and IFNgamma between groups I and II. Also, the levels of IL-4, IL-13, and TGFbeta1 were similar among the groups. The data indicate an elevation of Th1 cytokines in women with RM as compared to normal pregnant women, and IL-10 is an important cytokine in the maintenance of pregnancy.     

Role of CXCL9/CXCR3 chemokine biology during pathogenesis of acute lung allograft rejection

Acute allograft rejection is a major complication postlung transplantation and is the main risk factor for the development of bronchiolitis obliterans syndrome. Acute rejection is characterized by intragraft infiltration of activated mononuclear cells. The ELR-negative CXC chemokines CXCL9, CXCL10, and CXCL11) are potent chemoattractants for mononuclear cells and act through their shared receptor, CXCR3. Elevated levels of these chemokines in bronchoalveolar lavage fluid have been associated with human acute lung allograft rejection. This led to the hypothesis that the expression of these chemokines during an allogeneic response promotes the recruitment of mononuclear cells, leading to acute lung allograft rejection. We performed studies in a rat orthotopic lung transplantation model of acute rejection, and demonstrated increased expression of CXCL9 and CXCL10 paralleling the recruitment of mononuclear cells and cells expressing CXCR3 to the allograft. However, CXCL9 levels were 15-fold greater than CXCL10 during maximal rejection. Inhibition of CXCL9 decreased intragraft recruitment of mononuclear cells and cellular expression of CXCR3, resulting in lower acute lung allograft rejection scores. Furthermore, the combination of low dose cyclosporin A with anti-CXCL9 therapy had more profound effects on intragraft leukocyte infiltration and in reducing acute allograft rejection scores. This supports the notion that CXCL9 interaction with cells expressing CXCR3 has an important role in the recruitment of mononuclear cells, a pivotal event in the pathogenesis of acute lung allograft rejection.     

The roles of CD28 and CD40 ligand in T cell activation and tolerance

Costimulation of T cell activation involves both the B7:CD28 as well as the CD40 ligand (CD40L):CD40 pathway. To determine the importance of these pathways to in vitro and in vivo T cell activation, a direct comparison was made of the responses of TCR transgenic T cells lacking either CD28 or CD40L. In vitro, CD28-/- T cells showed a greater reduction in proliferative responses to Ag than did CD40L-/- T cells. The absence of CD28 resulted in defective Th2 responses, whereas CD40L-/- T cells were defective in Th1 development. In vivo, CD28-/- T cells failed to expand upon immunization, whereas CD40L-/- T cells could not sustain a response. These results suggest that CD28 is critical for initiating T cell responses, whereas CD40L is required for sustained Th1 responses. The different functional roles of these costimulatory pathways may explain why blocking B7:CD28 and CD40L:CD40 interactions has an additive effect in inhibiting T cell responses.     

Labdane diterpenes from Otostegia fruticosa

The new labdane diterpenes otostegin A (2), otostegin B (6) and 15-epi-otostegin B (7) were isolated from the aerial parts of Otostegia. fruticosa, besides the previously known labdanes preleoheterin (1), leoheterin (3), leopersin C and 15-epi-leopersin C (4, 5), ballonigrin (9) and vulgarol (11), along with the iridoid glucoside 8-O-acetylharpagide (10). The structure elucidation of all the isolated compounds was based on their spectral data and chemical derivatization.     

A novel spectrofluorimetric method for determination of lomefloxacin adopting on zinc(II) chelation strategy: Application in human plasma

A new sensitive and instantaneous spectrofluorimetric method for efficient determination of lomefloxacin (LMX) in its pure, dosage form and human plasma was designed. The developed method depends on formation of a metal-chelation compound of LMX as a ligand with zinc(II) in a buffer of acetate (pH 5.5). The following parameters; type of metal, concentration of metal, pH, type of buffer and diluting solvent were optimized. After carefully investigation; 0.2 mM zinc, 2.0 ml acetate buffer (pH 5.5) and water as diluting solvent were set as optimum reaction conditions. Under these conditions, a large increase in the intensity of the fluorescence of LMX was attained at 450 after excitation at 284 nm. The limits of detection and quantification were 5.8 and 1.9 ng ml⁻¹, respectively, with linearity range of 10.0 to 500.0 ng ml⁻¹. The binding mode of LMX and zinc(II) ion (Zn²⁺) was found to be 2:1, respectively, and confirmed by Job's plot method. Furthermore, it extended to the analysis of LMX in the spiked plasma of humans with percentage recovery (98.70 ± 0.97 to 100.30 ± 1.69%, n = 3).