Secreted IgM modulates IL-10 expression in B cells.

IL-10+ B cells are critical for immune homeostasis and restraining immune responses in infection, cancer, and inflammation; however, the signals that govern IL-10+ B cell differentiation are ill-defined. Here we find that IL-10+ B cells expand in mice lacking secreted IgM ((s)IgM-/-) up to 10-fold relative to wildtype (WT) among all major B cell and regulatory B cell subsets. The IL-10+ B cell increase is polyclonal and presents within 24 hours of birth. In WT mice, sIgM is produced prenatally and limits the expansion of IL-10+ B cells. Lack of the high affinity receptor for sIgM, FcµR, in B cells translates into an intermediate IL-10+ B cell phenotype relative to WT or sIgM-/- mice. Our study thus shows that sIgM regulates IL-10 programming in B cells in part via B cell-expressed FcµR, thereby revealing a function of sIgM in regulating immune homeostasis.

The strategic use of biopsy in the diagnosis of coeliac disease in adults.

BACKGROUND: The paediatric guidelines support the use of the 'No Biopsy Approach' in the diagnosis of coeliac disease (CD). We aimed to determine the correlation between anti tissue transglutaminase (anti-TTG serology) ≥10 times the upper limit of normal (ULN), using the Celikey ® ELiA assay and histological findings. Our secondary aim was to determine the safety of this approach in our centre. METHODS: A retrospective analysis of adult patients referred to a tertiary referral centre with raised anti-TTG titres and/or histological changes of coeliac on D2 biopsies between 2014 - 2019. Excluded patients were those who did not have a biopsy performed, or whose biopsy was unavailable for review, selective IgA deficiency, and gluten elimination prior to biopsy. Biopsies were classified according to Marsh, by two independent pathologists, blinded to the anti-TTG titre. RESULTS: 164 patients had positive anti-TTG serology and duodenal biopsy in our centre prior to starting a gluten free diet (GFD) in the period 2014 - 2019. Of these 164 patients (median age 40yrs, 62% female), 68 (33%) had an anti-TTG titre ≥10 x ULN, 99% of which had a Marsh grading ≥ 3 and 1% had a Marsh of 2 on biopsy. 91% had either a normal index gastroscopy or findings of mild gastritis/oesophagitis. CONCLUSIONS: We found a 98.5% positive predictive value (PPV) of determining CD (i.e., Marsh ≥ 3) in those with an anti-TTG ≥10 x ULN. In those with moderate to high-risk clinical suspicion of CD we propose that duodenal biopsy is unnecessary for diagnosis.

Pilot imaging of the colony stimulating factor 1 receptor in the brains of virally-suppressed individuals with HIV.

OBJECTIVE: Neuroimmune activation is a putative driver of cognitive impairment in people with HIV (PWH), even in the age of modern antiretroviral therapy. Nevertheless, imaging of the microglial marker, the 18 kDa translocator protein (TSPO), with positron emission tomography (PET) in treated PWH has yielded inconclusive findings. One potential reason for the varied TSPO results is a lack of cell-type specificity of the TSPO target. DESIGN: [ 11 C]CPPC, 5-cyano- N -(4-(4-[ 11 C]methylpiperazin-1-yl)-2-(piperidin-1-yl)phenyl) furan-2-carboxaminde, is a radiotracer for use with PET to image the colony stimulating factor 1 receptor (CSF1R). The CSF1R is expressed on microglia and central nervous system macrophages, with little expression on other cell types. We used [ 11 C]CPPC PET in virally-suppressed- (VS)-PWH and HIV-uninfected individuals to estimate the effect sizes of higher CSF1R in the brains of VS-PWH. METHODS: Sixteen VS-PWH and 15 HIV-uninfected individuals completed [ 11 C]CPPC PET. [ 11 C]CPPC binding (V T ) in nine regions was estimated using a one-tissue compartmental model with a metabolite-corrected arterial input function, and compared between groups. RESULTS: Regional [ 11 C]CPPC V T did not significantly differ between groups after age- and sex- adjustment [unstandardized beta coefficient ( B ) = 1.84, standard error (SE) = 1.18, P  = 0.13]. The effect size was moderate [Cohen's d  = 0.56, 95% confidence interval (CI) -0.16, 1.28), with strongest trend of higher V T in VS-PWH in striatum and parietal cortex (each P  = 0.04; Cohen's d  = 0.71 and 0.72, respectively). CONCLUSIONS: A group difference in [ 11 C]CPPC V T was not observed between VS-PWH and HIV-uninfected individuals in this pilot, although the observed effect sizes suggest the study was underpowered to detect regional group differences in binding.