Digital interventions for STI and HIV partner notification: a scoping review.

BACKGROUND: Partner notification (PN) is key to the control of sexually transmitted infections (STIs) and human immunodeficiency virus (HIV). Digital interventions have been used to facilitate PN. A scoping review was conducted to describe the interventions used, user preferences and acceptability of digital PN interventions from patient and partner perspectives. METHODS: A systematic literature search was conducted of eight databases for articles published in English, available online with digital PN outcome data. Articles were assessed using the Mixed Methods Appraisal Tool. Quantitative and qualitative data were synthesised and analysed using thematic analysis. RESULTS: Twenty-six articles met the eligibility criteria. Articles were heterogeneous in quality and design, with the majority using quantitative methods. Nine articles focused solely on bacterial STIs (five on syphilis; four on chlamydia), one on HIV, two on syphilis and HIV, and 14 included multiple STIs, of which 13 included HIV. There has been a shift over time from digital PN interventions solely focusing on notifying partners, to interventions including elements of partner management, such as facilitation of partner testing and treatment, or sharing of STI test results (between index patients and tested sex partners). Main outcomes measured were number of partners notified (13 articles), partner testing/consultation (eight articles) and treatment (five articles). Relationship type and STI type appeared to affect digital PN preferences for index patients with digital methods preferred for casual rather than established partner types. Generally, partners preferred face-to-face PN. CONCLUSION: Digital PN to date mainly focuses on notifying partners rather than comprehensive partner management. Despite an overall preference for face-to-face PN with partners, digital PN could play a useful role in improving outcomes for certain partner types and infections. Further research needs to understand the impact of digital PN interventions on specific PN outcomes, their effectiveness for different infections and include health economic evaluations.

Improving digital partner notification for sexually transmitted infections and HIV through a systematic review and application of the Behaviour Change Wheel approach.

BACKGROUND: Partner notification (PN) is key to controlling sexually transmitted infections (STIs) and human immunodeficiency virus (HIV). Digital PN options (e.g. social media, short message service (SMS), emails) are promising in increasing PN behaviour. However, their implementation is often challenging and studies report varied levels of acceptability and uptake of PN, highlighting the need to optimise digital PN interventions. METHODS: A systematic review of barriers and facilitators to digital PN interventions for STIs, including HIV, across eight research databases (from 2010 to 2023) identified eight relevant studies, two of which addressed HIV. Data extraction identified 98 barriers and 54 facilitators to the use of digital PN interventions. These were synthesised into 18 key barriers and 17 key facilitators that were each deemed amenable to change. We then used the Behaviour Change Wheel approach, the Acceptability, Practicability, Effectiveness, Affordability, Side-effects and Equity criteria, and multidisciplinary expert input, to systematically develop practical recommendations to optimise digital PN. RESULTS: Thirty-two specific recommendations clustered around three themes. Digital PN interventions should: (1) empower and support the index patient by providing a range of notification options, accompanied by clear instructions; (2) integrate into users' existing habits and the digital landscape, meeting contemporary standards and expectations of usability; and (3) address the social context of PN both online and offline through normalising the act of PN, combating STI-related stigma and stressing the altruistic aspects of PN through consistent messaging to service users and the public. CONCLUSIONS: Our evidence-based recommendations should be used to optimise existing digital PN interventions and inform the co-production of new ones.

Record DNA: reconceptualising digital records as the future evidence base.

A major issue facing society is the extent to which the usability of the digital evidence base is at risk because, in the digital era, the concept of the record has been eroded. The nature and reality of a record are no longer agreed. Addressing the challenges that the digital presents for managing records and assuring their future usability is not one that records and archives scholars and professionals can tackle alone. This article argues that this is a 'grand challenge' which requires a broad range of perspectives and expertise and convergence research to resolve. It discusses findings from an international multidisciplinary research network established to critically explore, through a grounded theory approach, the nature of a digital record and the implications of the digital era for the usability and functionality of the future evidence base. A series of different visions of a digital record emerged alongside a wide-ranging set of research questions that form the basis of an agenda for future collaborative (convergence) research.

A qualitative process evaluation using the behaviour change wheel approach: Did a whole genome sequence report form (SRF) used to reduce nosocomial SARS-CoV-2 within UK hospitals operate as anticipated?

PURPOSE: The aim of this study was to conduct a process evaluation of a whole-genome sequence report form (SRF) used to reduce nosocomial SARS-CoV-2 through changing infection prevention and control (IPC) behaviours within the COVID-19 pandemic. METHODS: We used a three-staged design. Firstly, we described and theorized the purported content of the SRF using the behaviour change wheel (BCW). Secondly, we used inductive thematic analysis of one-to-one interviews (n = 39) to explore contextual accounts of using the SRF. Thirdly, further deductive analysis gauged support for the intervention working as earlier anticipated. RESULTS: It was possible to theorize the SRF using the BCW approach and visualize it within a simple logic model. Inductive thematic analyses identified the SRF's acceptability, ease of use and perceived effectiveness. However, major challenges to embedding it in routine practice during the unfolding COVID-19 crisis were reported. Notwithstanding this insight, deductive analysis showed support for the putative intervention functions 'Education', 'Persuasion' and 'Enablement'; behaviour change techniques '1.2 Problem solving', '2.6 Biofeedback', '2.7 Feedback on outcomes of behaviour' and '7.1 Prompts and cues'; and theoretical domains framework domains 'Knowledge' and 'Behavioural regulation'. CONCLUSIONS: Our process evaluation of the SRF, using the BCW approach to describe and theorize its content, provided granular support for the SRF working to change IPC behaviours as anticipated. However, our complementary inductive thematic analysis highlighted the importance of the local context in constraining its routine use. For SRFs to reach their full potential in reducing nosocomial infections, further implementation research is needed.

Social Patterning and Stability of Intention to Accept a COVID-19 Vaccine in Scotland: Will Those Most at Risk Accept a Vaccine?

Vaccination is central to controlling COVID-19. Its success relies on having safe and effective vaccines and also on high levels of uptake by the public over time. Addressing questions of population-level acceptability, stability of acceptance, and sub-population variation in acceptability are imperative. Using a prospective design, a repeated measures two-wave online survey was conducted to assess key sociodemographic variables and intention to accept a COVID-19 vaccine. The first survey (Time 1) was completed by 3436 people during the period of national lockdown in Scotland and the second survey (n = 2016) was completed two months later (Time 2) when restrictions had been eased. In the first survey, 74% reported being willing to receive a COVID-19 vaccine. Logistic regression analyses showed that there were clear sociodemographic differences in intention to accept a vaccine for COVID-19 with intention being higher in participants of white ethnicity as compared with Black, Asian, and minority ethnic (BAME) groups, and in those with higher income levels and higher education levels. Intention was also higher in those who had "shielding" status due to underlying medical conditions. Our results suggest that future interventions, such as mass media and social marketing, need to be targeted at a range of sub-populations and diverse communities.

Engaging with change: Information and communication technology professionals' perspectives on change at the mid-point in the UK/EU Brexit process.

BACKGROUND: Information and Communication Technology (ICT) has been a key agent of change in the 21st century. Given the role of ICT in changing society, this research explores the responses and attitudes to change over time from ICT professionals and ICT academics in dealing with the potentially far reaching political challenge triggered by the UK's 2016 European Union Referendum and its decision to leave the European Union (Brexit). Whilst the vote was a UK based decision its ramifications have global implications and as such the research was not confined to the UK. This article presents the second phase of the research at the mid-point in the UK/European Union (EU) Brexit process, thus complementing the findings gathered immediately after the Referendum decision. The fundamental question being researched was: What are ICT professionals' personal and professional perspectives on the change triggered by Brexit in terms of opportunities and threats? METHODS AND FINDINGS: Data was collected through a survey launched in March 2018, one year on from the UK's triggering of Article 50 and marking the mid-point in the two-year Brexit process. The survey replicated the one delivered at the point of the Referendum decision in 2016 with some developments. In addition, two appreciative inquiry focus groups were conducted. The research sought to understand any shifting perspectives on the opportunities and threats that would exist post-Brexit for ICT professionals and academics. 59% of survey participants were negative regarding the Brexit decision. Participants noted the position post-Brexit for the UK, and the remaining 27 EU Member States (EU27), was still very uncertain at this stage. They observed that planned change versus uncertainty provides for very different responses. In spite of the uncertainty, the participants were able to consider and advocate for potential opportunities although these were framed from national perspectives. The opportunities identified within the appreciative inquiry focus groups aligned to those recorded by survey participants with similar themes highlighted. However, the optimum conditions for change have yet to be reached as there is still not an informed position, message and clear leadership with detailed information for the ICT context. Further data will be gathered after the UK exit from the EU, assuming this occurs.

Seventy Years of RN Effectiveness: A Database Development Project to Inform Best Practice.

BACKGROUND: The appropriate nursing staff mix is imperative to the provision of quality care. Nurse staffing levels and staff mix vary from country to country, as well as between care settings. Understanding how staffing skill mix impacts patient, organizational, and financial outcomes is critical in order to allow policymakers and clinicians to make evidence-informed staffing decisions. AIMS: This paper reports on the methodology for creation of an electronic database of studies exploring the effectiveness of Registered Nurses (RNs) on clinical and patient outcomes, organizational and nurse outcomes, and financial outcomes. METHODS: Comprehensive literature searches were conducted in four electronic databases. Inclusion criteria for the database included studies published from 1946 to 2016, peer-reviewed international literature, and studies focused on RNs in all health-care disciplines, settings, and sectors. Masters-prepared nurse researchers conducted title and abstract screening and relevance review to determine eligibility of studies for the database. High-level analysis was conducted to determine key outcomes and the frequency at which they appeared within the database. RESULTS: Of the initial 90,352 records, a total of 626 abstracts were included within the database. Studies were organized into three groups corresponding to clinical and patient outcomes, organizational and nurse-related outcomes, and financial outcomes. Organizational and nurse-related outcomes represented the largest category in the database with 282 studies, followed by clinical and patient outcomes with 244 studies, and lastly financial outcomes, which included 124 studies. LINKING EVIDENCE TO ACTION: The comprehensive database of evidence for RN effectiveness is freely available at https://rnao.ca/bpg/initiatives/RNEffectiveness. The database will serve as a resource for the Registered Nurses' Association of Ontario, as well as a tool for researchers, clinicians, and policymakers for making evidence-informed staffing decisions.

Engaging with change: Information and communication technology professionals' perspectives on change in the context of the 'Brexit' vote.

BACKGROUND: Information and Communication Technology (ICT) has been a key agent of change in the 21st century. Given the role of ICT in changing society this research sought to explore the responses and attitudes to change from ICT professionals and ICT academics in dealing with the potentially far reaching political challenge triggered by the UK's 2016 European Union Referendum and its decision to leave the European Union (referred to as Brexit). Whilst the vote was a UK based decision its ramifications have global implications and as such the research was not confined to the UK. METHODS AND FINDINGS: Data was collected through a survey launched on the first working day after the Brexit referendum vote to leave the EU and kept open for four weeks. The survey contained qualitative and quantitative questions. It sought to understand the opportunities and threats that would exist post-Brexit for ICT professionals and academics triggered by the decision. The research captured a complex rich picture on ICT professionals' responses to the potential challenge of change triggered by the Brexit vote. Immediately after the Brexit decision the research reveals uncertainties amongst ICT professionals regarding what the decision would mean, with just under half of the participants not identifying any opportunities or threats. For those who did, threats outweighed opportunities by just more than double. Whilst understanding the global possibilities and dangers, participants saw their position from national and organizational perspectives. The highest frequency coded threats related to areas outside the participants' control and the highest frequency opportunities related to areas where there was the potential for ICT interventions. This survey is part of longitudinal piece of research. Using the same methodological approach two further surveys are planned. The second survey will be one year after Article 50 was triggered on 29 March 2017. The final survey will be one year after the UK exit from the EU, assuming this occurs.

Use of whole blood for analysis of disease-associated biomarkers.

Analyses for diagnosis and monitoring of pathological conditions often rely on blood samples, partly due to relative ease of collection. However, many interfering substances largely preclude the use of whole blood itself, necessitating separation of plasma or serum. We present a feasibility study demonstrating potential use of fresh or frozen whole blood to detect soluble biomarkers using an enzyme-linked immunosorbent assay (ELISA)-based method. Good correlation between levels of soluble CD25 in plasma and whole blood of healthy individuals or Alzheimer's patients was established. These results provide a basis for development of a novel biosensor approach for disease-associated biomarker detection in whole blood.

Dendritic cell migration assay: a potential prediction model for identification of contact allergens.

This manuscript describes methodology and a prediction model for the MUTZ-LC migration assay. The assay represents the physiological change in Langerhans cell (LC) behavior after exposure to a sensitizing chemical, resulting in LC migration from the epidermis to the dermis. MUTZ-LC are derived from the commercially available MUTZ-3 cell line. Upon exposure to a sensitizer MUTZ-LC migrate preferentially towards CXCL12 whereas upon exposure to a non-sensitizer MUTZ-LC migrate towards CCL5. A CXCL12/CCL5 ratio >1.10 in 2/3 independent experiments is indicative of a sensitizer, whereas a CXCL12/CCL5 ratio ≤1.10 is indicative of a non-sensitizer. At non cytotoxic chemical concentrations 9 sensitizers (2,4-dinitrochlorobenzene, paraphenylendiamine, cinnamaldehyde, isoeugenol, nickel-sulfate, tetramethylthiuram disulfide, eugenol, cinnamic-alcohol, ammonium-hexachloroplatinate) were distinguished from 4 non sensitizers (sodium lauryl sulfate, salicylic acid, phenol, octanoic acid). Critical points in assay performance are (i) MUTZ-3 passage number after thawing (p6-p40); (ii) cell viability (>80%); (iii) standard curve to optimize correlation of fluorescence with cell number; and (iv) optimization of the concentration of rhCXCL12 and rhCCL5 in transwell. The protocol has been tested in three European laboratories and results suggest that it may provide working conditions for performing the DC migration assay which is aimed at distinguishing sensitizers from non sensitizers.

Adrenomedullin receptors on human T cells are glucocorticoid-sensitive.

Adrenomedullin (AM) is a novel vasodilatatory peptide which acts primarily through the calcitonin receptor-like receptor (CLR) in combination with either receptor-activity-modifying-protein (RAMP) 2 or 3 (forming receptors, AM(1) and AM(2) respectively). AM plays an important role during inflammation, with its expression increasing following cytokine treatment, promoting macrophage action in situ and high expression by T cells during hypoxic conditions. Examination of T cell AM receptor expression has previously been incomplete, hence we here consider the presentation of AM receptors and their responsiveness to AM and glucocorticoids (GC). AM receptor expression was examined by PCR and flow cytometry in primary human T cells, revealing that RAMP2, 3 and CLR are physiologically expressed in unstimulated T cells, both intracellularly and on the cell surface. PHA stimulation decreased receptor proteins, significantly so for CLR and RAMP3. Incubation with AM elicited limited receptor alterations however, GC treatment (10(-6) M; 24 h) markedly affected cell surface expression, significantly increasing receptor components in unstimulated cells and significantly decreasing the same in stimulated T cells. Our findings indicate that human T cells utilize both AM(1) and AM(2) receptors, which are GC-sensitive in an activation-state dependent manner.

Identification of PDL-1 as a novel biomarker of sensitizer exposure in dendritic-like cells.

The development of novel in vitro methods to assess risks of allergic sensitization are essential in reducing animal testing whilst maintaining consumer safety. The main research objectives of this study were to identify novel biomarkers to assess the sensitization predictability of chemicals. Phenotypic and cytokine responses of moDCs and MUTZ-3 cells were investigated following application of contact sensitizers; dinitrochlorobenzene (DNCB), cinnamaldehyde (Cin), eugenol (E), isoeugenol (IE), P-phenylenediamine (PPD) and non-sensitizers; salicyclic acid (SA) and sodium lauryl sulphate (SLS). CD86 was up-regulated on MUTZ-3 cells in response to DNCB, Cin and PPD, however, moDCs only modulated CD86 in response to DNCB and E. PDL-1 (Programmed death receptor ligand-1) proved a promising sensitization biomarker in MUTZ-3 cells where up-regulation occurred in response to DNCB, Cin, IE and PPD. Additionally, moDC-expressed PDL-1 was modulated in response to Cin, IE and E thus demonstrating improved sensitizer predictability when compared with CD86. MCP-1 and RANTES were identified as biomarkers of DNCB exposure but MCP-1 did not show any change in expression above controls for the other sensitizers investigated. However, RANTES was increased in MUTZ-3 cells by both DNCB and Cin. Our findings highlight novel biomarkers which, in MUTZ-3 cells, could be taken forward within a multiple biomarker in vitro assay ensuring strong and reliable predictability.

Nociceptin-induced modulation of human T cell function.

There is an accumulating evidence for the immunoregulatory role of the neuropeptide, nociceptin/orphanin FQ (N/OFQ) however its role on T cell function requires elucidation. This study has demonstrated an inhibitory role for N/OFQ on SEB-activated T cell function. N/OFQ decreases T cell proliferation, which is abrogated when the costimulatory receptors CD80 and CD86 are blocked. In addition, evidence suggests that the immunoregulatory cytokines TGF-beta, IFN-gamma and nitric oxide (NO) are involved in the N/OFQ effect. N/OFQ also, through involvement of IFN and NO, induces the expression of the immunosuppressive modulator indoleamine 2,3-dioxygenase (IDO), suggesting a central role for IDO in the N/OFQ effect on T cell proliferation. The data presented in this report indicate a multi-faceted mechanism of action used by N/OFQ to modulate T cell function.

Apoptotic cells induce dendritic cell-mediated suppression via interferon-gamma-induced IDO.

Dendritic cells (DC) are sensitive to their local environment and are affected by proximal cell death. This study investigated the modulatory effect of cell death on DC function. Monocyte-derived DC exposed to apoptotic Jurkat or primary T cells failed to induce phenotypic maturation of the DC and were unable to support CD4+ allogeneic T-cell proliferation compared with DC exposed to lipopolysaccharide (LPS) or necrotic cells. Apoptotic cells coincubated with LPS- or necrotic cell-induced mature DC significantly suppressed CD80, CD86 and CD83 and attenuated LPS-induced CD4+ T-cell proliferation. Reduced levels of interleukin-12 (IL-12), IL-10, IL-6, tumour necrosis factor-alpha and interferon-gamma (IFN-gamma) were found to be concomitant with the suppressive activity of apoptotic cells upon DC. Furthermore, intracellular staining confirmed IFN-gamma expression by DC in association with apoptotic environments. The specific generation of IFN-gamma by DC within apoptotic environments is suggestive of an anti-inflammatory role by the induction of indoleamine 2,3-dioxygenase (IDO). Both neutralization of IFN-gamma and IDO blockade demonstrated a role for IFN-gamma and IDO in the suppression of CD4+ T cells. Moreover, we demonstrate that IDO expression within the DC was found to be IFN-gamma-dependent. Blocking transforming growth factor-beta (TGF-beta) also produced a partial release in T-cell proliferation. Our study strongly suggests that apoptosis-induced DC suppression is not an immunological null event and two prime mediators underpinning these functional effects are IFN-gamma-induced IDO and TGF-beta.

A review of in vitro modelling approaches to the identification and modulation of squamous metaplasia in the human tracheobronchial epithelium.

Squamous metaplasia in the tracheobronchial epithelium (TBE) involves the replacement of the normal pseudostratified mucociliary epithelium with a stratified squamous epithelium. Squamous metaplasia is considered to be an adaptive response that protects the lumen from the effects of inhaled airborne pollutants, but which might also feature as a pre-neoplastic lesion preceding squamous cell carcinoma. With the exception of transglutaminase I, involucrin, and cytokeratins 5, 6 and 13, few markers that contribute to the squamous phenotype have been identified in human TBE that can be used in diagnosis or to monitor its development in laboratory investigations, and current models are inadequate to provide statistically meaningful data. Therefore, new predictive markers have been identified, and new techniques established, in epithelial in vitro models capable of expressing squamous characteristics, which will be used to identify hazardous exposures and elucidate the mechanisms by which they induce their effects. A protocol for the quantitative detection of transglutaminase activity has been standardised in keratinocytes, based on the enzymatic incorporation of fluorescein-cadaverine (FC) into bis(gamma-glutamyl) polyamine cross-links. The specificity of this compound as a transglutaminase substrate was demonstrated by using a range of competitive transglutaminase inhibitors, and by modulation of the squamous pathway. FC incorporation was localised to the cell membrane of terminally differentiating cells, and was not visible in basal, proliferating cells. High calcium-containing medium, nicotine and cigarette smoke condensates (CSC) induced an increase in FC incorporation, providing evidence of their role in enhancing the squamous pathway. Analysis by flow cytometry was used to provide a quantitative assessment of a range of optimised squamous differentiation markers, identified in normal human bronchial epithelia and in a bronchial cell line. Transglutaminase I was induced in a time-dependent manner, in post-confluent cells induced to differentiate down the squamous pathway, whereas involucrin was ubiquitously expressed and the levels of cytokeratins 5, 6 and 18 were reduced. The response of these and other differentiation markers to squamous-inducing conditions is being explored.

Engineering anticancer T cells for extended functional longevity.

Like other somatic cells, human T lymphocytes have a finite replicative capacity in vitro, and, by implication and consistent with the limited data available, in vivo as well. An accumulation of dysfunctional T cells may be detrimental under conditions of chronic antigenic stress (chronic infection, cancer, autoimmunity). Using T cells from young donors to model the process of T cell clonal expansion in vitro under these conditions reveals age-associated increasing levels of oxidative DNA damage and microsatellite instability (MSI), coupled with decreasing DNA repair capacity, telomerase induction and telomere length, decreased levels of expression of the T cell costimulator CD28 and consequently reduced secretion of the T cell growth factor interleukin-2 (IL-2). However, data from similar experiments using T cell clones (TCCs) derived from extremely healthy very elderly donors ("successfully aged") indicate that DNA repair is better maintained, MSI less prevalent, and (already short) telomere lengths are maintained. Nonetheless, oxidative DNA damage is seen to the same extent, and clonal longevity is also similar in these clones. DNA damage levels are reduced by culture in 5% oxygen, but longevity is not improved. This may be because of the requirement for intermittent reactivation via receptor pathways dependent on free radical production in T cells. These recent findings from our international immunosenescence research consortium suggest that strategies other than telomere maintenance, better protection against free radicals, or improved DNA repair will be required for functional longevity extension of human TCCs. To obtain sufficient cells for adoptive immunotherapy of cancer, alternative avenues need exploration; currently, these include enforced expression of certain heat shock proteins and proteasome components, and interference with the expression of negative regulatory receptors expressed by T cells.

Activation marker expression and apoptotic susceptibility of T-cell clones derived from CD34(+), young and SENIEUR donors.

T-cell clones (TCC) derived from human peripheral blood lymphocytes of a young control, a healthy elderly (SENIEUR) donor, or from CD34(+) hematopoietic progenitor cells were utilised in this study to examine how in vivo and in vitro ageing affects T-cell apoptotic capability. The role of CD25, CD28 and the intracellular proteins, FLICE-inhibitory protein (FLIP), receptor-interacting protein (RIP) and caspase 3 were investigated. We observed an age-related decline in the expression of the IL-2 receptor alpha chain CD25, and absence of the co-stimulatory receptor CD28 on three of the four TCC studied. In young donor- and CD34 cell-derived TCC, but not in SENIEUR donor-derived TCC, we observed an age-related increase in susceptibility of the cells to mFas-L-induced apoptosis, which correlated with the age-related decrease of CD25 expression. Expression levels of full-length RIP and FLIP did not show any correlation to apoptotic susceptibility. However, expression levels of the cleaved form of RIP were greatly reduced in the SENIEUR donor-derived TCC, which together with a trend towards increased caspase 3 activity, could indicate an age-related alteration in utilisation of different apoptotic signalling pathways.

Nociceptin/orphanin FQ modulates human T cell function in vitro.

Although nociceptin/orphanin FQ (N/OFQ) and its receptor (ORL-1) are widely distributed throughout the immune system, its role has yet to be elucidated. This study shows that N/OFQ (10(-14)-10(-12) M) modulates T cell activation by up-regulating activation marker expression, e.g. CD28, leading to enhanced proliferation and modulation of TNFalpha secretion. However, on re-stimulated T cells N/OFQ causes inhibition of proliferation, which could be linked with N/OFQ up-regulating CTLA-4 expression. We have also shown that some of these effects are partly prostaglandin-dependent and that N/OFQ induces prostaglandin synthesis. This report suggests that N/OFQ could exert a key modulatory role in human T cell functions.

Identification of a secondary zinc-binding site in staphylococcal enterotoxin C2. Implications for superantigen recognition.

The previously determined crystal structure of the superantigen staphylococcal enterotoxin C2 (SEC2) showed binding of a single zinc ion located between the N- and C-terminal domains. Here we present the crystal structure of SEC2 determined to 2.0 A resolution in the presence of additional zinc. The structure revealed the presence of a secondary zinc-binding site close to the major histocompatibility complex (MHC)-binding site of the toxin and some 28 A away from the primary zinc-binding site of the toxin found in previous studies. T cell stimulation assays showed that varying the concentration of zinc ions present affected the activity of the toxin and we observed that high zinc concentrations considerably inhibited T cell responses. This indicates that SEC2 may have multiple modes of interaction with the immune system that are dependent on serum zinc levels. The potential role of the secondary zinc-binding site and that of the primary one in the formation of the TCR.SEC2.MHC complex are considered, and the possibility that zinc may regulate the activity of SEC2 as a toxin facilitating different T cell responses is discussed.

P-glycoprotein decreases with T cell maturation but is not responsible for resistance to CD95-induced apoptosis.

P-glycoprotein (Pgp) is a membrane transporter responsible for resistance to chemotherapy in cancer cells. Its presence in T cells is very well documented, but its function in the immune system is still poorly understood. Recent findings suggest that Pgp may be involved in regulating programmed cell death by inhibiting caspase 8 and caspase 3. Utilising antigenically-activated T cells and the physiologically relevant apoptotic ligand, membrane CD95-L, we have previously reported that while T cells are generally resistant to CD95-induced death at early stages of activation, their susceptibility to apoptosis increases with successive activation and clonal expansion. In this study we investigated whether changes in apoptotic susceptibility were related to T cell Pgp function. Results showed that Pgp expression and function in T cells decreases with maturation, with CD8 cells having the highest Pgp function. However, although Pgp function inversely correlated with caspase 3 activity, no difference was observed between apoptotic susceptible CD25- cells and resistant CD25+ cells. In addition sorting of cells with high and low Pgp function showed no correlation with apoptotic capability. Therefore, whilst Pgp modulates caspase activity, it is not responsible for resistance to apoptosis of early activated T cells nor the increased susceptibility observed at the later stages of maturation in antigenically activated cells.