Quantitative Multiplexed Imaging Analysis Reveals a Strong Association between Immunogen-Specific B Cell Responses and Tonsillar Germinal Center Immune Dynamics in Children after Influenza Vaccination.

Generation of Ag-specific humoral responses requires the orchestrated development and function of highly specialized immune cells in secondary lymphoid organs. We used a multiparametric approach combining flow cytometry, confocal microscopy, and histocytometry to analyze, for the first time to our knowledge in children, tonsils from seasonal influenza-vaccinated children. We used these novel imaging assays to address the mucosal immune dynamics in tonsils investigating the spatial positioning, frequency, and phenotype of immune cells after vaccination. Vaccination was associated with a significantly higher frequency of follicular helper CD4 T cells compared with the unvaccinated control group. The imaging analysis revealed that potential suppressor (FOXP3hi) CD4 T cells are mainly located in extrafollicular areas. Furthermore, a significantly reduced frequency of both follicular and extrafollicular FOXP3hi CD4 T cells was found in the vaccine group compared with the control group. Levels of circulating CXCL13 were higher in those vaccinated compared with controls, mirroring an increased germinal center reactivity in the tonsils. Notably, a strong correlation was found between the frequency of tonsillar T follicular helper cells and tonsillar Ag-specific Ab-secreting cells. These data demonstrate that influenza vaccination promotes the prevalence of relevant immune cells in tonsillar follicles and support the use of tonsils as lymphoid sites for the study of germinal center reactions after vaccination in children.

Unusual presentation of haemophilia in two paediatric patients.

Haemophilia A is a rare X-linked recessive bleeding disorder caused by deficiency or functional defects in coagulation factor VIII (FVIII). Here, we report two cases of challenging diagnosis of haemophilia A because of unusual presentation. The first case is a 10-month-old female, admitted to our hospital because a neck mass appeared within the previous 24 h, who had a past medical history consistent with recurrent spontaneous haematomas but no family history of bleeding disorders. Despite several radiological evaluations, only the histology of the mass defined the presence of a haematoma. Chromosomal analysis revealed a normal female karyotype and a de-novo mutation into the FVIII intron 22 associated with a skewed X chromosome inactivation. The second case is a male neonate with a history of seizures who underwent brain MRI that showed a suspicious vascular malformation on the quadrigeminal cistern, causing cerebellum compression and hydrocephalus. The clinical conditions of the child progressively worsened and blood tests revealed a severe deficit of FVIII levels. The radiological images were re-evaluated; vascular anomalies were excluded and the diagnosis of haematoma was made. Family history was negative for coagulation disorders. Molecular studies revealed a rearrangement of the FVIII gene involving intron 22. The haemophilia A diagnosis can be challenging. Lack of family history, difficulties in detecting haematomas by imaging techniques, female sex and neonatal age represent misleading factors that can delay the diagnosis.