Increased Ig-null B lymphocytes in the peripheral blood of pediatric solid organ transplant recipients with elevated Epstein-Barr viral loads

: In this study, the characteristics of Ig‐null B cells in high viral load carriers were examined by four‐color flow cytometry. The frequency of Ig‐null B cells in patients with high, low or undetectable virus loads was found that while patients with a high load had more Ig‐null cells, these cells were also present in the low and undetectable load groups. As Ig‐null cells from patients with no viral load were EBV‐negative, EBV infection was not absolutely required for the generation or survival of Ig‐null cells. Ig‐null cells were CD19+, sIg‐, CD5−, CD10−, CD27−, CD23−, CD38−, and CD69− with variable surface expression of CD20 and CD40. Ig‐null cells did not have a proliferating cell phenotype (Ki67‐) and a high proportion were HLA class I‐ and class II‐. Virus copy number in CD19+ Ig‐null cell populations may be much higher than in CD19+ Ig+ cell populations. EBV infected Ig‐null cells were common in blood specimens from pediatric solid organ transplant recipients and infected Ig‐null cells may pose potential problems for immunotherapies that target infected B cells directly.