Role of B Cells in Breaking and Maintaining Tolerance to Clotting Factor VIII in Congenital and Acquired Hemophilia A

The effect of T helper (Th)/T cytotoxic (Tc) ratio on disease severity in type A hemophilia patients

BACKGROUND AND OBJECTIVES

The aim of this study was to investigate the T helper (Th) to T cytotoxic (Tc) ratio in children suffering from type A hemophilia disease and to evaluate the correlation of this ratio with disease severity.

MATERIAL AND METHOD

Two mls of EDTA anti coagulated whole blood was collected. Immunophenotyping of lymphocytes count was carried out by FACS analysis using a double CD4 and CD8 kit. The mean ± SD of absolute numbers of CD4 and CD8 lymphocytes/ml was calculated and the ratio of CD4/CD8 was evaluated by statistical method.

RESULTS

Among 80 type A hemophilia patients, 66 (82.5%) were male. The mean age was 15 ± 3.51 years. 12 (15%) of them were suffering from mild disease and 68 (85%) had sever disease. The CD4 /CD8 ratio was obtained between 0.45 and 1.44 with mean1.79 ± 0.78. The correlation between this ration and disease severity was 0.019.

CONCLUSION

The results showed that CD4/CD8 ratio has correlation with disease severity in type A hemophilia patients, however there was no association between this ratio and gender.

Regulatory B Cells Are Functionally Impaired in Patients Having Hemophilia A With Inhibitors

Development of inhibitors remains a major clinical complication in patients with hemophilia A receiving replacement therapy with factor VIII (FVIII). Understanding the immune mechanisms involved in the development of inhibitors can provide valuable information about pathways to human tolerance. Recent evidence indicates that B regulatory (Breg) cells play a pivotal role in controlling the production of antibodies (Abs) while promoting follicular T helper (Tfh) cells and monocytes, expressing the low-density lipoprotein receptor-related protein (LRP/CD91), which is involved in FVIII intake from the circulation. We studied circulating levels of Breg cells along with Tfh cells and the expression of LRP/CD91 on monocytes in patients with hemophilia A using 8-color flow cytometry and cell culture. Compared to healthy controls, patients with hemophilia A with inhibitors showed a severe reduction in levels of Breg cells and produced less interleukin-10 when activated via the CD40 signaling pathway. In addition, patients with hemophilia A with inhibitors exhibited an overexpression of LPR/CD91 on monocytes and normal levels of Tfh cells. Levels of Breg cells were not significantly related to LPR/CD91 although negative associations were evidenced. Collectively, these results provide new insights into the role of Breg cells and LPR/CD91 in the development of inhibitors in patients with hemophilia A.