The cell biology of major histocompatibility complex class I assembly: towards a molecular understanding

Major histocompatibility complex class I (MHC I) proteins protect the host from intracellular pathogens and cellular abnormalities through the binding of peptide fragments derived primarily from intracellular proteins. These peptide-MHC complexes are displayed at the cell surface for inspection by cytotoxic T lymphocytes. Here we reveal how MHC I molecules achieve this feat in the face of numerous levels of quality control. Among these is the chaperone tapasin, which governs peptide selection in the endoplasmic reticulum as part of the peptide-loading complex, and we propose key amino acid interactions central to the peptide selection mechanism. We discuss how the aminopeptidase ERAAP fine-tunes the peptide repertoire available to assembling MHC I molecules, before focusing on the journey of MHC I molecules through the secretory pathway, where calreticulin provides additional regulation of MHC I expression. Lastly we discuss how these processes culminate to influence immune responses.

Validity of self-reported solar UVR exposure compared with objectively measured UVR exposure

BACKGROUND

Reliance on verbal self-report of solar exposure in skin cancer prevention and epidemiologic studies may be problematic if self-report data are not valid due to systematic errors in recall, social desirability bias, or other reasons.

METHODS

This study examines the validity of self-reports of exposure to ultraviolet radiation (UVR) compared to objectively measured exposure among children and adults in outdoor recreation settings in 4 regions of the United States. Objective UVR exposures of 515 participants were measured using polysulfone film badge UVR dosimeters on 2 days. The same subjects provided self-reported UVR exposure data on surveys and 4-day sun exposure diaries, for comparison to their objectively measured exposure.

RESULTS

Dosimeter data showed that lifeguards had the greatest UVR exposure (24.5% of weekday ambient UVR), children the next highest exposures (10.3% ambient weekday UVR), and parents had the lowest (6.6% ambient weekday UVR). Similar patterns were observed in self-report data. Correlations between diary reports and dosimeter findings were fair to good and were highest for lifeguards (r = 0.38-0.57), followed by parents (r = 0.28-0.29) and children (r = 0.18-0.34). Correlations between survey and diary measures were moderate to good for lifeguards (r = 0.20-0.54) and children (r = 0.35-0.53).

CONCLUSIONS

This is the largest study of its kind to date, and supports the utility of self-report measures of solar UVR exposure.

IMPACT

Overall, self-reports of sun exposure produce valid measures of UVR exposure among parents, children, and lifeguards who work outdoors.

Individual and setting level predictors of the implementation of a skin cancer prevention program: a multilevel analysis

BACKGROUND

To achieve widespread cancer control, a better understanding is needed of the factors that contribute to successful implementation of effective skin cancer prevention interventions. This study assessed the relative contributions of individual- and setting-level characteristics to implementation of a widely disseminated skin cancer prevention program.

METHODS

A multilevel analysis was conducted using data from the Pool Cool Diffusion Trial from 2004 and replicated with data from 2005. Implementation of Pool Cool by lifeguards was measured using a composite score (implementation variable, range 0 to 10) that assessed whether the lifeguard performed different components of the intervention. Predictors included lifeguard background characteristics, lifeguard sun protection-related attitudes and behaviors, pool characteristics, and enhanced (i.e., more technical assistance, tailored materials, and incentives are provided) versus basic treatment group.

RESULTS

The mean value of the implementation variable was 4 in both years (2004 and 2005; SD = 2 in 2004 and SD = 3 in 2005) indicating a moderate implementation for most lifeguards. Several individual-level (lifeguard characteristics) and setting-level (pool characteristics and treatment group) factors were found to be significantly associated with implementation of Pool Cool by lifeguards. All three lifeguard-level domains (lifeguard background characteristics, lifeguard sun protection-related attitudes and behaviors) and six pool-level predictors (number of weekly pool visitors, intervention intensity, geographic latitude, pool location, sun safety and/or skin cancer prevention programs, and sun safety programs and policies) were included in the final model. The most important predictors of implementation were the number of weekly pool visitors (inverse association) and enhanced treatment group (positive association). That is, pools with fewer weekly visitors and pools in the enhanced treatment group had significantly higher program implementation in both 2004 and 2005.

CONCLUSIONS

More intense, theory-driven dissemination strategies led to higher levels of implementation of this effective skin cancer prevention program. Issues to be considered by practitioners seeking to implement evidence-based programs in community settings, include taking into account both individual-level and setting-level factors, using active implementation approaches, and assessing local needs to adapt intervention materials.

Measured occupational solar UVR exposures of lifeguards in pool settings

BACKGROUND

The aim of this study was to measure ultraviolet radiation (UVR) exposures of lifeguards in pool settings and evaluate their personal UVR protective practices.

METHODS

Lifeguards (n = 168) wore UVR sensitive polysulfone (PS) film badges in wrist bracelets on 2 days and completed a survey and diary covering sun protection use. Analyses were used to describe sun exposure and sun protection practices, to compare UVR exposure across locations, and to compare findings with recommended threshold limits for occupational exposure.

RESULTS

The measured UVR exposures varied with location, ranging from high median UVR exposures of 6.2 standard erythemal doses (SEDs) to the lowest median of 1.7 SEDs. More than 74% of the lifeguards' PS badges showed UVR above recommended threshold limits for occupational exposure. Thirty-nine percent received more than four times the limit and 65% of cases were sufficient to induce sunburn. The most common protective behaviors were wearing sunglasses and using sunscreen, but sun protection was often inadequate.

CONCLUSIONS

At-risk individuals were exposed to high levels of UVR in excess of occupational limits and though appropriate types of sun protection were used, it was not used consistently and more than 50% of lifeguards reported being sunburnt at least twice during the previous year.

A controlled trial of objective measures of sunscreen and moisturizing lotion

Taking an alcohol swab of a person's forearm and analyzing it using a spectrophotometer has been shown to be a reliable method for detecting the presence of sunscreen. The aims of this study were to determine if moisturizing lotions or other non-sunscreen products influence the absorbance readings from skin swabs in a controlled setting, and to establish the cutoff point in determining the presence or absence of sunscreen using a crystal cuvette instead of a plastic one. In a controlled trial of 30 volunteer office workers, absorbance readings from two popular brands of sunscreen with sun-protection factors (SPF) of 30 and 45 were compared with absorbance readings from two different moisturizing lotions, one with an SPF of 15 and another with no stated SPF. Moisturizers with SPF 15 tested positive for sunscreen, with absorbance readings (mean, 3.77; min, 3.30) comparable to sunblock with SPF 30 or 45 (mean, 3.51; min, 2.02). Moisturizers with no stated SPF factor tested negative for the presence of sunscreen, with extremely low absorbance readings (mean, 0.06; max, 0.19) similar to control readings. The skin swabbing technique remains a valid and useful method for detecting the presence of sunscreen and does not result in false positives when moisturizers with no stated SPF are present. Using a conservative cutoff point of 0.30 with a crystal cuvette reduces any chance of false-positive readings and remains robust when sunscreen of SPF 15 or higher is present.

Characteristics of swimming pools with high rates of objectively measured sunscreen use

BACKGROUND

A combination of verbal reports, observations, and physical assessments can improve understanding of prevention programs.

OBJECTIVE

Skin swabbing techniques were used to detect the presence of sunscreen as part of a sun protection measurement study at 16 swimming pools. Three pools demonstrated much higher sunscreen use (>95%) than the others (47.1%). This paper compares these three pools to the other 13 to examine whether they have common features and if different sources of data can help interpret the findings.

METHODS

Data were collected from skin swabs detecting the presence of sunscreen; observations of participants; observations of pool environments; and surveys.

RESULTS

Pool observations showed a higher use of shade structures, sun safety signs, and other supporting items at the three high-sunscreen use pools. These three pools had significantly more year-round and long-term employees than did the other 13 pools.

LIMITATIONS

Sunscreen characteristics could not be determined using the swabbing technique. Publicity about the study, or the weather, may have influenced behaviors at the pools.

CONCLUSIONS

Supportive environments were associated with consistent high levels of sunscreen use. This study also confirms the importance of using multiple data sources to interpret findings.

Lifeguards' sun protection habits and sunburns: association with sun-safe environments and skin cancer prevention program participation

OBJECTIVE

To examine associations among outdoor pool environments, social norms, pool policies, and participation in a sun safety program with lifeguards' sun protection habits and sunburn.

DESIGN

Cross-sectional survey.

SETTING

Outdoor swimming pools across the United States.

PARTICIPANTS

Lifeguards and aquatic instructors at pools participating in the Pool Cool skin cancer prevention program in 2001 (N = 699) and 2002 (N = 987).

MAIN OUTCOME MEASURES

Sun protection habits and number of sunburns.

RESULTS

Social norms supporting sun safety were associated with more sun protection habits (95% confidence intervals [CIs], 0.18-0.28 in 2001 and 0.17-0.26 in 2002), as were pool policies supporting sun safety (95% CI, 0.02-0.07 in 2001 and 0.002-0.04 in 2002). There was a trend toward fewer sunburns as social norms, pool policies, and participation in the Pool Cool program increased, but results differed across the 2 years. In 2001, lower social norms scores and pool policy scores were associated with more reported sunburns. In 2002, teaching Pool Cool sun safety lessons was associated with fewer sunburns.

CONCLUSION

The pool environment is related to sun safety behaviors of outdoor pool staff, with social norms showing the strongest association.

Long-term outcome of using allopurinol co-therapy as a strategy for overcoming thiopurine hepatotoxicity in treating inflammatory bowel disease

BACKGROUND

Hepatotoxicity results in the withdrawal of thiopurines drugs, azathioprine (AZA) and mercaptopurine (MP), in up to 10% of patients with inflammatory bowel disease. Our group previously demonstrated that allopurinol with AZA/ciclosporin/steroid 'triple therapy' improved renal graft survival.

AIM

To confirm the hypothesis that allopurinol may alleviate thiopurine hepatotoxicity by similar mechanisms as proposed in our renal study.

METHODS

Unselected patients with acute thiopurine hepatotoxicity were offered allopurinol co-therapy with low-dose AZA or MP. The starting AZA/MP dose was determined by thiopurine methyltransferase (TPMT) activity (two patients were intermediate TPMT); then this dose was reduced to 25% for allopurinol co-therapy. Response to treatment was assessed by clinical severity indices, endoscopy and blood tests.

RESULTS

Of 11 patients (three Crohn's disease, eight ulcerative colitis) treated, nine (82%) remain in long-term remission (median 42 months) with normal liver tests. One patient also successfully bypassed flu-like symptoms. Two stopped: one nausea, one abnormal liver function (stealosis on biopsy). Leucopenia occurred in two cases and resolved with minor dose reductions.

CONCLUSIONS

Allopurinol co-therapy with low-dose AZA/MP can alleviate thiopurine hepatotoxicity. It appears safe and effective for long-term use, but requires monitoring for myelotoxicity. Assessing the TPMT activity helps tailor the AZA/MP doses.

Can a transitional work grant program in a workers' compensation system reduce cost and facilitate return to work?

Although previous research has shown returning the injured worker to work as soon as possible is important to the long-term prospects of the worker remaining in the work force, there is limited economic support for implementing such programs. Thus, the purpose of this case control study was to determine the cost savings of the implementation of a Transitional Work Grant (TWG) program, which consisted of several components including job analyses, education, communication and transitional work (TW). Companies that enrolled in the TWG program were matched to nonparticipating companies (NTW) based on employer size, type of industry, number of overall claims, and number of claims with > 7 days lost time (LT claims) submitted the year prior to enrollment. The study analyzed economic data: number of claims, number of LT claims, indemnity costs, medical costs, and days lost (days away from the workplace). An additional outcome was the ratio of LT claims (> 7 days lost work) to medical only (MO) claims (LT/MO ratio). Overall, participation in the TWG program was associated with decreased indemnity cost and decreased LT/MO ratio. However, effectiveness of the program varied by employer size and industry. In terms of the state of Ohio, these costs translate into substantial savings: more than $2.3 million per year. Although the cost savings and reduction in lost time claims is encouraging, the true benefit of TW has yet to be completely quantified. Future work must account for other potential co-factors and programs that could also contribute to the savings as well as document further the indirect benefits associated with a TWG program, such as improved employee morale and increased productivity and product quality that could be four times greater than the direct savings. In summary, programs such as this one adopted by several companies in Ohio can reduce the cost burden of injuries.

Process evaluation of the Pool Cool Diffusion Trial for skin cancer prevention across 2 years

Though process evaluation of health programs has received growing attention, few interventions have reported process evaluation over multiple years. This article describes 2 years of process evaluation (2003-04) for the Pool Cool Diffusion Trial. Pool Cool is a skin cancer prevention program designed to increase sun protection habits among children and improve organizational and environmental supports for sun protection at swimming pools. Each year, 80 telephone interviews and 40 site visits at pools across the United States were completed, to examine how fully the program was implemented and the extent of use of program components between the two study conditions. Major components of the Pool Cool program, including sun safety lessons, sun safety signs and sunscreen use, had high implementation. Between the 2 years, most of the core elements were either maintained or increased in use. There were no significant differences between the basic and enhanced conditions on implementation. Reasons given for successful implementation were the provision of a toolkit, ease of implementing the program, pool staff and children enjoying the program and the field coordinators' support. These data provide information on programmatic factors that contribute to successful program diffusion.

What is the significance of a positive Propionibacterium acnes culture around a joint replacement?

The purpose of this study was to show the significance of a positive Propionibacterium acnes sample around a joint replacement. Records from the microbiology laboratory data over a 3-year period were reviewed to identify patients with prosthetic joints from whom Propionibacterium acnes was isolated at least once. The medical records of all those patients were retrieved and the demographic, clinical, microbiological and haematological data were collected and examined. The preoperative values of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were recorded. Fifty patients underwent a routine revision of a joint arthroplasty; six patients had a joint aspiration. Only one patient had further revision surgery for infection. The preoperative values of ESR and CRP were very variable. The presence of a positive sample around a joint arthroplasty is of uncertain significance. Further studies are needed in order to establish uniform criteria for the diagnosis of infection caused by Propionibacterium acnes.

Candida infective endocarditis

Candida infective endocarditis (IE) is uncommon but often fatal. Most epidemiologic data are derived from small case series or case reports. This study was conducted to explore the epidemiology, treatment patterns, and outcomes of patients with Candida IE. We compared 33 Candida IE cases to 2,716 patients with non-fungal IE in the International Collaboration on Endocarditis-Prospective Cohort Study (ICE-PCS). Patients were enrolled and the data collected from June 2000 until August 2005. We noted that patients with Candida IE were more likely to have prosthetic valves (p < 0.001), short-term indwelling catheters (p < 0.0001), and have healthcare-associated infections (p < 0.001). The reasons for surgery differed between the two groups: myocardial abscess (46.7% vs. 22.2%, p = 0.026) and persistent positive blood cultures (33.3% vs. 9.9%, p = 0.003) were more common among those with Candida IE. Mortality at discharge was higher in patients with Candida IE (30.3%) when compared to non-fungal cases (17%, p = 0.046). Among Candida patients, mortality was similar in patients who received combination surgical and antifungal therapy versus antifungal therapy alone (33.3% vs. 27.8%, p = 0.26). New antifungal drugs, particularly echinocandins, were used frequently. These multi-center data suggest distinct epidemiologic features of Candida IE when compared to non-fungal cases. Indications for surgical intervention are different and mortality is increased. Newer antifungal treatment options are increasingly used. Large, multi-center studies are needed to help better define Candida IE.

A pilot study of the validity of self-reported ultraviolet radiation exposure and sun protection practices among lifeguards, parents and children

Outdoor recreation settings, such as swimming pools, provide a promising venue to assess UVR exposure and sun protection practices among individuals who are minimally clothed and exposed to potentially high levels of UVR. Most studies assessing sun exposure/protection practices rely on self-reported data, which are subject to bias. The aim of this study was to establish the feasibility of conducting a multimethod study to examine the validity of self-reported measures within a swimming pool setting. Data were collected from 27 lifeguards, children and parents in Hawaii. Each participant filled out a survey and a 4 day sun habits diary. On two occasions, researchers assessed observable sun protection behaviors (wearing hats, shirts, sunglasses), swabbed the skin to detect the presence of sunscreen, and subjects wore polysulphone dosimeters to measure UVR exposure. Overall, observed sun protection behaviors were more highly correlated with diary reports than with survey reports. While lifeguards and children reported spending comparable amounts of time in the sun, dosimeter measures showed that lifeguards received twice as much UVR exposure. This study demonstrated the feasibility of implementing a multimethod validity study within a broader population of swimming pools.

Diffusion of an effective skin cancer prevention program: design, theoretical foundations, and first-year implementation

This article describes the design and theoretical foundations of the Pool Cool Diffusion Trial and reports 1st-year findings. Aims of the study are to evaluate the effects of 2 strategies for diffusion of the Pool Cool sun safety program on implementation, maintenance, and sustainability; improvements in environmental supports for sun safety in swimming pools; and sun protection habits and sunburn among participating children. There was a high rate of program participation (86.6%; n=375 swimming pools) in the 1st year and somewhat lower study participation (75.8%). Analysis of pool manager surveys revealed a time effect for overall sun safety programs and for sun safety policies, environmental strategies, and programs for pool users. There were few differences in implementation between treatment groups in year one.