Characteristics and influencing factors of CD19+ B cell reconstitution in patients following haploidentical/mismatched hematopoietic stem cell transplantation

In patients undergoing hematopoietic stem cell transplantation (HSCT), B cells exert important, prolonged effects that provide protection from infection. In this study, we analyzed characteristics and influencing factors of CD19+ B cell reconstitution in 83 patients who underwent unmanipulated haploidentical/mismatched blood and bone marrow transplantation. Of these patients, 45 % showed a normal CD19+ B cell count at +360 days. Factors associated with lower CD19+ B cell levels were as follows: aGVHD grades II–IV had a trend to affect CD19+ B cell reconstitution at +180 days; clinically extensive cGVHD was significantly associated with CD19+ B cell deficiency at +360 days and serum IgG level at +180 and +360 days; cytomegalovirus (CMV) infection occurred after +38 days was correlated with lower B cell level at both +90 and +360 days, while those occurred before +38 days did not show this effect; glucocorticoids used around +90 and +180 days was associated with lower CD19+ B cell levels at +90 and +360 days, respectively, especially in patients that did not experience extensive cGVHD. In contrast, the number of HLA-mismatched locus positively correlated with CD19+ B cell at +90 days and serum IgG level at +180 days. In conclusion, CD19+ B cell recovery after haploidentical/mismatched HSCT was mainly influenced by GVHD and/or its treatment, CMV infection that occurred later (after +38 days) and use of glucocorticoids. Improvement of B cell recovery is likely to be achieved through effective prophylaxis of GVHD, minimized use of glucocorticoids, and preemptive treatment of CMV infection occurring after +38 days. More HLA-mismatched loci may initiate a stronger humoral response toward alloantigens >180 days after HSCT, which may be beneficial for the eradication of minimal residual disease and protection from infection.