P450s (cytochrome P450 mono-oxygenases) are a superfamily of haem-containing mono-oxygenase enzymes that participate in a wide range of biochemical pathways in different organisms from all of the domains of life. To facilitate their activity, P450s require sequential delivery of two electrons passed from one or more redox partner enzymes. Although the P450 enzymes themselves show remarkable similarity in overall structure, it is increasingly apparent that there is enormous diversity in the redox partner systems that drive the P450 enzymes. This paper examines some of the recent advances in our understanding of the biodiversity of the P450 redox apparatus, with a particular emphasis on the redox systems in the pathogen Mycobacterium tuberculosis.

The diverse origins, nanometre‐scale and invasive isolation procedures associated with extracellular vesicles (EVs) mean they are usually studied in bulk and disconnected from their parental cell. Here, we used super‐resolution microscopy to directly compare EVs secreted by individual human monocyte‐derived macrophages (MDMs). MDMs were differentiated to be M0‐, M1‐ or M2‐like, with all three secreting EVs at similar densities following activation. However, M0‐like cells secreted larger EVs than M1‐ and M2‐like macrophages. Proteomic analysis revealed variations in the contents of differently sized EVs as well as between EVs secreted by different MDM phenotypes. Super resolution microscopy of single‐cell secretions identified that the class II MHC protein, HLA‐DR, was expressed on ∼40% of EVs secreted from M1‐like MDMs, which was double the frequency observed for M0‐like and M2‐like EVs. Strikingly, human macrophages, isolated from the resected lungs of cancer patients, secreted EVs that expressed HLA‐DR at double the frequency and with greater intensity than M1‐like EVs. Quantitative analysis of single‐cell EV profiles from all four macrophage phenotypes revealed distinct secretion types, five of which were consistent across multiple sample cohorts. A sub‐population of M1‐like MDMs secreted EVs similar to lung macrophages, suggesting an expansion or recruitment of cells with a specific EV secretion profile within the lungs of cancer patients. Thus, quantitative analysis of EV heterogeneity can be used for single cell profiling and to reveal novel macrophage biology.

A 61-year-old man was referred to the interstitial lung disease (ILD) clinic in April 2014 with a 7-year history of dry cough and progressive breathlessness despite immunosuppressive therapy, leading to a reduction in exercise tolerance from over 10 kilometres to 20 metres. He had a prior diagnosis since 2009 of HP based on high-resolution CT (HRCT) and biopsy findings from his referring hospital. He did not have any exposure to birds or pigeons. His house showed no evidence of mould or water damage, and he had no symptoms of connective tissue disease. The precipitating trigger for his HP was unknown. His symptoms were insidious and progressive, with the exception of a 3-month period in 2011 when he went to live in Australia. He reported that during this time his symptoms rapidly improved and that he was able to walk 10 kilometres on the beach without stopping. On returning to the UK, his breathing deteriorated rapidly. There was no significant medical history. He was a lifelong non-smoker. As a hobby, he played the bagpipes daily. He did not take his bagpipes to Australia. He had been treated with prednisolone 0.5 mg/kg, which had been intermittently tapered to maintain symptomatic stability. Prior to clinic review, the case was reviewed in an ILD multidisciplinary team meeting (MDT). Serial HRCT images demonstrated progressive ground-glass change and mosaic pattern. Lung function demonstrated a severe restrictive deficit with FVC of 1.48 (34%), a 38% decline over a 5-year period and diffusing capacity for carbon monoxide (DLCO) of 3.21 (33%). This had deteriorated progressively since diagnosis in 2009 when the FVC was 2.39 (56%) and DLCO was 4.89 (50%). Despite his severe restriction in lung function, he continued to play the bagpipes daily and did not require home oxygen therapy. Lung biopsy in 2009 showed upper lobe interstitial fibrosis and poorly formed granulomas. An MDT diagnosis of HP with unknown trigger was made based upon clinical history, HRCT scan and histological findings. Following specialist ILD assessment of progressive symptoms, radiological findings and of worsening restrictive lung deficit, he was commenced on 2 mg/kg azathioprine combined with maintenance prednisolone. He continued to play the bagpipes daily.