Genetic interaction between the non-homologous end-joining factors during B and T lymphocyte development: In vivo mouse models

Non-homologous end joining (NHEJ) is the main DNA repair mechanism for the repair of double-strand breaks (DSBs) throughout the course of the cell cycle. DSBs are generated in developing B and T lymphocytes during V(D)J recombination to increase the repertoire of B and T cell receptors. DSBs are also generated during the class switch recombination (CSR) process in mature B lymphocytes, providing distinct effector functions of antibody heavy chain constant regions. Thus, NHEJ is important for both V(D)J recombination and CSR. NHEJ comprises core Ku70 and Ku80 subunits that form the Ku heterodimer, which binds DSBs and promotes the recruitment of accessory factors (e.g., DNA-PKcs, Artemis, PAXX, MRI) and downstream core factors (XLF, Lig4 and XRCC4). In recent decades, new NHEJ proteins have been reported, increasing complexity of this molecular pathway. Numerous in vivo mouse models have been generated and characterized to identify the interplay of NHEJ factors and their role in development of adaptive immune system. This review summarizes the currently available mouse models lacking one or several NHEJ factors, with a particular focus on early B cell development. We also underline genetic interactions and redundancy in the NHEJ pathway in mice.     

The prevalence of pain at pressure areas and pressure ulcers in hospitalised patients

Background

Patients with pressure ulcers (PUs) report that pain is their most distressing symptom, but there are few PU pain prevalence studies. We sought to estimate the prevalence of unattributed pressure area related pain (UPAR pain) which was defined as pain, soreness or discomfort reported by patients, on an “at risk” or PU skin site, reported at a patient level.

Methods

We undertook pain prevalence surveys in 2 large UK teaching hospital NHS Trusts (6 hospitals) and a district general hospital NHS Trust (3 hospitals) during their routine annual PU prevalence audits. The hospitals provide secondary and tertiary care beds in acute and elective surgery, trauma and orthopaedics, burns, medicine, elderly medicine, oncology and rehabilitation. Anonymised individual patient data were recorded by the ward nurse and PU prevalence team. The analysis of this prevalence survey included data summaries; no inferential statistical testing was planned or undertaken. Percentages were calculated using the total number of patients from the relevant population as the denominator (i.e. including all patients with missing data for that variable).

Results

A total of 3,397 patients in 9 acute hospitals were included in routine PU prevalence audits and, of these, 2010 (59.2%) patients participated in the pain prevalence study. UPAR pain prevalence was 16.3% (327/2010). 1769 patients had no PUs and of these 223 patients reported UPAR pain, a prevalence of 12.6%. Of the 241 people with pressure ulcers, 104 patients reported pain, a UPAR pain prevalence of 43.2% (104/241).

Conclusion

One in six people in acute hospitals experience UPAR pain on ‘at risk’ or PU skin sites; one in every 8 people without PUs and, more than 2 out of every five people with PUs. The results provide a clear indication that all patients should be asked if they have pain at pressure areas even when they do not have a PU.

     

Health service use in Rett syndrome

Rett syndrome is a severe neurodevelopmental disorder affecting girls, caused by mutations in the MECP2 gene. There are no population-based data on the extent and determinants of health service use in this disorder. The population-based registry, the Australian Rett Syndrome database, was the source of phenotype data. This also contains data from mutation screening and X-inactivation studies. Data on retrospective (n = 152) and prospective (n = 162) health service use were collected in 2000 from a questionnaire and a calendar study, respectively. Health service use was highest in younger cases (P = .001) and lowest in cases with milder phenotypes (P < .001). Random X-inactivation was associated with service use (P = .02). Maternal education, phenotype, and individual mutations were determinants of health service use. The use of a retrospective and prospective data set enabled accurate assessment of service use in Rett syndrome. Both genetic and sociodemographic determinants of health service use were identified, with important implications for the optimal and equitable management of children with Rett syndrome.     

Gamma interferon responses induced by a panel of recombinant and purified mycobacterial antigens in healthy,non-mycobacterium bovis BCG-vaccinated Malawian young adults

We have previously shown that young adults living in a rural area of northern Malawi showed greater gamma interferon (IFN-gamma) responses to purified protein derivatives (PPD) prepared from environmental mycobacteria than to PPD from Mycobacterium tuberculosis. In order to define the mycobacterial species to which individuals living in a rural African population have been exposed and sensitized, we tested T-cell recognition of recombinant and purified antigens from M. tuberculosis (38 kDa, MPT64, and ESAT-6), M. bovis (MPB70), M. bovis BCG (Ag85), and M. leprae (65 kDa, 35 kDa, and 18 kDa) in >600 non-M. bovis BCG-vaccinated young adults in the Karonga District of northern Malawi. IFN-gamma was measured by enzyme-linked immunosorbent assay (ELISA) in day 6 supernatants of diluted whole-blood cultures. The recombinant M. leprae 35-kDa and 18-kDa and purified native M. bovis BCG Ag85 antigens induced the highest percentages of responders, though both leprosy and bovine tuberculosis are now rare in this population. The M. tuberculosis antigens ESAT-6 and MPT64 and the M. bovis antigen MPB70 induced the lowest percentages of responders. One of the subjects subsequently developed extrapulmonary tuberculosis; this individual had a 15-mm-diameter reaction to the Mantoux test and responded to M. tuberculosis PPD, Ag85, MPT64, and ESAT-6 but not to any of the leprosy antigens. We conclude that in this rural African population, exposure to M. tuberculosis or M. bovis is much less frequent than exposure to environmental mycobacteria such as M. avium, which have antigens homologous to the M. leprae 35-kDa and 18-kDa antigens. M. tuberculosis ESAT-6 showed the strongest association with the size of the Mantoux skin test induration, suggesting that among the three M. tuberculosis antigens tested it provided the best indication of exposure to, or infection with, M. tuberculosis.