Higher proportions of peripheral CD19+CD5+ B cells predict the effect of corticosteroid in patients with late-onset hemorrhagic cystitis after allogeneic hematopoietic stem cell transplantation. 
The cause of late-onset hemorrhagic cystitis (LOHC) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains obscure.  In clinical practice, some LOHC patients respond to immunosuppression.  The aim of this study was to determine the immune pathogenesis of LOHC post allo-HSCT.  With the diagnosis of LOHC, patients were given initial treatment consisting of fluid hydration, alkalization and forced diuresis, and empirical anti-viral therapy for 10 - 14 days or until a week after the virus became negative.  The nonresponders were applied corticosteroid.  Seven to ten days later, patients' response was evaluated.  Along with treatment, CD19(+) B lymphocyte subsets were measured at various study points.  From October 2009 to March 2010, we found 28 cases of LOHC occurred in 25 patients who underwent allo-HSCT in our hospital.  Except that three cases were not treated according to the protocol, the other 25 cases were divided into three groups: anti-virus responders (Group A, n = 6), corticosteroid responders (Group B1, n = 16), corticosteroid and anti-virus nonresponders (Group C, n = 3) according to their clinical response.  Percentages of CD19(+)CD5(+) B lymphocytes were not significantly different among three groups at onset of LOCH.  However, in Group B1 after the first anti-virus phase, percentages of CD19(+)CD5(+) lymphocytes significantly increased comparing with those at onset (P = 0.022), and then significantly decreased at PR (P = 0.003) and CR (P = 0.002) with corticosteroid treatment.  But significant change was not observed in Groups A and C. The immune etiology seems to be involved in the development of LOHC and the proportion of CD19(+)CD5(+) lymphocytes may serve as a cellular biomarker to predict the response to corticosteroid in LOHC.