Efficient Expansion of Human Granzyme B-Expressing B Cells with Potent Regulatory Properties.

Granzyme B-expressing B cells have been shown to be an important regulatory B cell subset in humans. However, it is unclear which subpopulations of B cells express GZMB under normal conditions and which protocols effectively induce ex vivo expansion of GZMB+ B cells. We found that in the peripheral blood of normal individuals, plasmablasts were the major B cell subpopulation that expressed GZMB. However, when using an in vitro plasmablast differentiation protocol, we obtained only 2% GZMB+ B cells. Nevertheless, using an expansion mixture containing IL-21, anti-BCR, CpG oligodeoxynucleotide, CD40L, and IL-2, we were able to obtain more than 90% GZMB+ B cells after 3 d culture. GZMB+ B cells obtained through this protocol suppressed the proliferation of autologous and allogenic CD4+CD25- effector T cells. The suppressive effect of GZMB+ B cells was partially GZMB dependent and totally contact dependent but was not associated with an increase in effector T cell apoptosis or uptake of GZMB by effector T cells. Interestingly, we showed that GZMB produced by B cells promoted GZMB+ B cell proliferation in ERK1/2-dependent manner, facilitating GZMB+ B cell expansion. However, GZMB+ B cells tended to undergo apoptosis after prolonged stimulation, which may be considered a negative feedback mechanism to limit their uncontrolled expansion. Finally, we found that expanded GZMB+ B cells exhibited a regulatory phenotype and were enriched in CD307bhi, CD258hiCD72hi, and CD21loPD-1hi B cell subpopulations. Our study, to our knowledge, provides new insight into biology of GZMB+ B cells and an efficient method to expand GZMB+ B cells for future cell therapy applications.

Bone Scintigraphy After a Negative Radiological Skeletal Survey Improves the Detection Rate of Inflicted Skeletal Injury in Children.

Background: Timely diagnosis of child physical abuse is of paramount importance. The added value of bone scintigraphy (BS) after a negative radiological skeletal survey (RSS) in children with suspected physical abuse has never been evaluated. Objective: The objective of this study was to assess the extent to which BS could improve the detection rate of skeletal injury in children with suspected physical abuse with an initial negative RSS. Methods: We used discharge codes to retrospectively identify children evaluated for suspected physical abuse in a university hospital (Nantes, France). We included all consecutive children younger than 3 years old who underwent both RSS and BS, with an interval of ≤96 h between tests, from 2013 to 2019. BS and RSS results were interpreted independently during the study period. We specifically analyzed BS results for children with a negative RSS to assess the value of BS as an add-on test. Results: Among the 268 children ≤3 years old with suspected physical abuse who underwent RSS, 140 (52%) also underwent BS within 96 h and were included in the analysis. The median age was 6 months old (interquartile range: 3-8). The detection rate of ≥1 skeletal injury with RSS alone was 49% (n = 69/140, 95% CI: 41-58%) vs. 58% (n = 81/140, 50-66%) with RSS followed by add-on BS, for an absolute increase in the detection rate of 9% points (95% CI: 4-14%). The number of children with a negative RSS who would need to undergo BS to detect one additional child with ≥1 skeletal injury was 6 (95% CI: 4-11). Conclusion: In young children with suspected physical abuse with a negative RSS, add-on BS would allow for a clinically significant improvement in the detection rate of skeletal injuries for a limited number of BS procedures required. Prospective multicenter studies are needed to confirm these findings.