source: American Society of Pediatric Hematology/Oncology

year: 2017

authors: Mohamed-Rachid Boulassel, Amal Al-Naamani, Zahra Al-Qarni, Hanan Nazir, Ahmed Al-Yarabi, Mohammad Hunieni, Abdulhakim Al-Rawas, Yasser Wali

Splenectomy is the mainstay of long-term management of sickle cell disease (SCD) patients with frequent splenic sequestration crisis. However, it exposes patients to increased risk of infections, which remain major concern for both patients and clinicians. Dendritic cells (DC) play a key role in priming immune responses against infections. To date, limited information is available about DC subsets and their clinical relevance in splenectomised children with SCD.

A total of 57 SCD children who underwent open splenectomy were prospectively enrolled. Twenty eight age- and sex-matched healthy children were recruited as controls. The indication of splenectomy was based on the history of patients, clinical examination, hematological and radiological findings. The circulating DC subsets including plasmacytoid DC (pDC) and myeloid DC (mDC) were phenotypically identified by the expression of HLA-DR, CD123, CD11c, Lin and CD1d surface markers using 8-color flow cytometry. The B cell subsets were characterized by the positive staining with CD19, CD24 and CD38 surface markers. Comparisons among study groups were performed using unpaired t test, while the Spearman’s correlation was used to assess associations.

Compared to healthy controls, splenectomised children exhibited significantly lower levels of pDC (P=0.02). Similarly, levels of mDC were significantly reduced in splenectomised children compared to healthy controls (0.009). Interestingly, levels of pDC expressing CD1d, a non-classical molecule that is critical for generating cytokines from innate cells, were significantly reduced in splenectomised children compared to healthy controls (P<0.001).

Levels of memory B cells, but not total and naïve B cells, were also significantly lower in splenectomised children compared to healthy controls (P=0.02). The levels of pDC and mDC were weakly associated with memory B cells (r=0.41, P=0.04), but not with age, total hemoglobin levels at phlebotomy, baseline haemoglobin F, time since splenectomy, hydroxyurea therapy and clinical severity.

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