Top row is a schematic representation of the variable domain of the IGH chain derived from the rearrangement of an IGHV (green), an IGHD (red), and an IGHJ (orange) gene. Dotted areas represent complementarity determining regions (CDR1-3). Full areas represent framework regions (FR1-4). One to 3 different approaches for allele-specific oligonucleotide RQ-PCR are represented (see text for details). Consensus primers and probes are depicted in blue. CDR3-specific primers and probes are depicted in orange.