The relationship between antibody concentration and target cell number in the induction of K cell-mediated haemolysis: evidence for asymmetry among reactants

The cytotoxic capacity of peripheral blood mononuclear cells for anti-D sensitized human O Rh(D) + ve (R1R2) erythrocytes was measured under conditions where antibody concentrations and target cell number were varied with respect to each other. It was observed that where sensitization was limiting, due either to target cell excess or increased antibody dilution, the relationship between lysis and antibody concentration was non-linear, and that the end-point dilution of anti-D at which measurable cytotoxicity occurred was dependent upon the source or concentration of effector cells. The asymmetrical relationship between cytotoxic activity and the degree of sensitization suggests that, in this system at least, there is extensive heterogeneity either among target erythrocytes in terms of their degree of sensitization and consequent susceptibility to lysis, and/or among effector cells in terms of their sensitization requirements for induction of cytotoxicity.     

Influence of lectin-free interleukin-2 on natural and antibody-dependent cellular cytotoxicity

Supernatants derived from MLA-144, a gibbon T cell line that constitutively releases interleukin-2 (IL-2) and which lack detectable interferon (IFN) had the capacity to enhance the natural killer (NK) cells function of human peripheral blood lymphocytes. Percoll fractionation revealed that like IFN-inducible cytotoxic cells lymphocytes responding to MLA-144 supernatants cofractionate with native NK cells. Exposure to MLA-144 conditioned medium also potentiated the cytotoxic capacity of extravascular effector cells which are either unresponsive or weakly responsive to interferon-alpha (IFN-alpha). Moreover lymphocyte (K cell)-mediated antibody-dependent cellular cytotoxicity (ADCC) which is unresponsive to IFN-alpha was in most cases subject to a modest potentiation following treatment with MLA-144 supernatants. These data confirm previous reports that IL-2 can regulate peripheral blood NK cell function and also demonstrate that this lymphokine can also influence those natural cytotoxic mechanisms which are unresponsive to IFN-alpha.     

小儿腹腔镜胆囊切除术的效果,安全性和费用分析

目的 :分析腹腔镜胆囊切除术 (LC)在儿外科实践的效率。方法 :回顾性研究两所儿童医疗中心开展儿童LC(1 993年 3月～ 2 0 0 0年 5月 )的效果 ,安全性和费用材料。统计分析用Student’st检验。结果 :1 1 8例胆囊切除术中 ,32例OC(2 7% ) ,86例LC(73 % )中 ,3例中转OC(3 .5 % )。手术时间LC =96 .3min与OC =96 .7min ,P >0 .0 5。住院时间LC比OC减少 2 .8d ,P <0 .0 5。两组均无手术技术并发症。LC总费用与OC比较没有明显增加 ,LC是 (30 4 2 9± 897)元与OC是 (30 2 4 5± 6 842 )元 ,P =0 .91。结论 :LC应用于儿童安全而有效。LC明显缩短了住院时间。经过培养的医生做LC ,不会增加并发症。与OC比较 ,LC不增加医疗费用     

Skin irritation, false positives and the local lymph node assay: a guideline issue?

Since the formal validation and regulatory acceptance of the local lymph node assay (LLNA) there have been commentaries suggesting that the irritant properties of substances can give rise to false positives. As toxicology aspires to progress rapidly towards the age of in vitro alternatives, it is of increasing importance that issues relating to assay selectivity and performance are understood fully, and that true false positive responses are distinguished clearly from those that are simply unpalatable. In the present review, we have focused on whether skin irritation per se is actually a direct cause of true false positive results in the LLNA. The body of published work has been examined critically and considered in relation to our current understanding of the mechanisms of skin irritation and skin sensitisation. From these analyses it is very clear that, of itself, skin irritation is not a cause of false positive results. The corollary is, therefore, that limiting test concentrations in the LLNA for the purpose of avoiding skin irritation may lead, unintentionally, to false negatives. Where a substance is a true false positive in the LLNA, the classic example being sodium lauryl sulphate, explanations for that positivity will have to reach beyond the seductive, but incorrect, recourse to its skin irritation potential.     

Substrate binding by a bacterial ABC transporter involved in polysaccharide export

ATP-binding-cassette (ABC) transporters are responsible for the export of a wide variety of cell-surface glycoconjugates in both Gram-positive and Gram-negative bacteria. These include the O-antigenic polysaccharide (O-PS) portion of lipopolysaccharide, a crucial virulence determinant in Gram-negative pathogens. O-PSs are synthesized by one of two fundamentally different pathways. Escherichia coli O serotypes O8 and O9a provide the prototype systems for studying O-PS export via ABC transporters. The transporter is composed of the transmembrane component Wzm and the nucleotide-binding component Wzt. Although the N-terminal domain of Wzt is a conventional ABC protein, the C-terminal domain of Wzt (C-Wzt) is a unique structural element that determines the specificity of the transporter for either the O8 or O9a O-PS. We show here that the two domains of Wzt can function when expressed as separate polypeptides; both are essential for export. In vitro, C-Wzt binds its cognate O-PS by recognizing a residue located at the nonreducing end of the polymer. The crystal structure of C-Wzt(O9a) is reported here and reveals a beta sandwich with an immunoglobulin-like topology that contains the O-PS-binding pocket. Substrate interactions with nucleotide-binding domains have been demonstrated in an ABC exporter previously. However, to our knowledge substrate binding by a discrete, cytoplasmic accessory domain in an extended nucleotide-binding domain polypeptide has not previously been demonstrated. Elucidation of the substrate-recognition system involved in O-PS export provides insight into the mechanism that coordinates polymer biosynthesis, termination, and export.     

Atopic dermatitis and allergic reactions to individual fragrance chemicals

Background:  Allergic contact dermatitis prevalence is reported as equal in atopic and nonatopic dermatitis. Atopic dermatitis is under‐represented in those with allergic contact dermatitis to agents having cutaneous and dietary exposure. We compared rates of atopic dermatitis between patients with allergic contact dermatitis arising out of individual fragrance chemicals with known oral/cutaneous exposure against exclusively cutaneous exposure. Methods:  Between 1982 and 2007, 37 065 dermatitis patients were tested with Fragrance mix I. Those who were positive were tested for individual fragrance allergy. Chemicals were categorized according to whether their exposure pattern was solely cutaneous, oral or mixed. Current and past atopic dermatitis rates were compared between the whole population and groups allergic to individual fragrances. Age and gender were controlled. Results:  Cinnamic alcohol and cinnamal allergy groups had reduced rates of both ‘current’ [24/266 (9.0%) P = 0.0008, 38/364 (10.4%) P = 0.0005] and ‘past’ atopic dermatitis [44/266 (16.5%) P = 0.009, 70/346 (19.2%) P = 0.037]. Atopic dermatitis rates in groups allergic to Evernia prunastri and hydroxycitronellal (cutaneous exposure only) were not reduced [120/597 (20.1%) and 41/153 (26.8%)]. Groups allergic to cinnamic alcohol (P < 0.0001, P < 0.0001) and cinnamal (P < 0.0001, P < 0.004) had reductions in ‘current’ and ‘past’ atopic dermatitis, compared with Evernia prunastri. Conclusions:  Patients allergic to individual fragrances with dietary exposure have reduced rates of atopic dermatitis. This suggests that patients with atopic dermatitis have heightened oral tolerance to dietary haptens, in contrast to the known close association of atopic dermatitis with food‐protein allergy. Haptens may interfere with food protein tolerance by binding to soluble protein to alter its configuration and immunogenic profile.     

Biological evaluation of intervertebral disc cells in different formulations of gellan gum‐based hydrogels

Gellan gum (GG)‐based hydrogels are advantageous in tissue engineering not only due to their ability to retain large quantities of water and provide a similar environment to that of natural extracellular matrix (ECM), but also because they can gelify in situ in seconds. Their mechanical properties can be fine‐tuned to mimic natural tissues such as the nucleus pulposus (NP). This study produced different formulations of GG hydrogels by mixing varying amounts of methacrylated (GG‐MA) and high‐acyl gellan gums (HA‐GG) for applications as acellular and cellular NP substitutes. The hydrogels were physicochemically characterized by dynamic mechanical analysis. Degradation and swelling abilities were assessed by soaking in a phosphate buffered saline solution for up to 170 h. Results showed that as HA‐GG content increased, the modulus of the hydrogels decreased. Moreover, increases in HA‐GG content induced greater weight loss in the GG‐MA/HA‐GG formulation compared to GG‐MA hydrogel. Potential cytotoxicity of the hydrogel was assessed by culturing rabbit NP cells up to 7 days. An MTS assay was performed by seeding rabbit NP cells onto the surface of 3D hydrogel disc formulations. Viability of rabbit NP cells encapsulated within the different hydrogel formulations was also evaluated by Calcein‐AM and ATP assays. Results showed that tunable GG‐MA/HA‐GG hydrogels were non‐cytotoxic and supported viability of rabbit NP cells. Copyright © 2012 John Wiley & Sons, Ltd.