Sensitive flow cytometric analysis of PBMC of a healthy control and the patient with the 631delT RAG1 gene.

Based on scatter characteristics, gating was performed on lymphocytes (A and B). To further reduce background staining in our attempts to detect rare events (CD19⁺ B cells), we used a so-called exclusion gate with negativity for labeling with the PE-conjugated CD3, CD14, CD15, CD16, and CD56 antibodies (C and D). This exclusion of T-lymphocytes, monocytes, granulocytes, and NK cells resulted in the sensitive detection of CD19⁺ B-lymphocytes. The patient had less than 0.01% CD19⁺ B-lymphocytes (F); the healthy control had 22% (E).