Flow cytometric analysis of thawed BM samples from 5 RAG-deficient SCID patients compared to 2 healthy children.

The precursor B-cell compartment was analyzed within a lymphocyte gate and a CD19⁺ gate, which was purified by exclusion of cells expressing CD3, CD16, or CD33. (A) Analysis of CD10 and CD20 expression within the purified CD19⁺ lymphocyte gate. (B) Analysis of Cylgμ and SmlgM expression within the purified CD19⁺lymphocyte gate. (C) Analysis of Cylgμ and CyVpreB expression within the purified lymphocyte gate. The sequential order of the B-cell differentiation stages is indicated with arrows in the youngest healthy child. The composition of the precursor B-cell compartment in the 2 healthy children was representative of that in other healthy children (n = 6). In general, RAG-deficient SCID patients lacked the more mature B-cell differentiation stages with a strong relative increase in the immature B-cell differentiation stages. According to Nomura et al, expression of CyVpreB precedes expression of CD19.45Within a CD19⁺ lymphocyte gate, all cells should thus be CyVpreB⁺ or CyIgμ⁺ (C). Therefore, we suggest that the double-negative events represent apoptotic cells. The age at BM sampling is indicated.