Figure 1.

H-CDR3 spectratypes of the V_H6 or V_H3.15 transcripts expressed by the blood B cell subsets of two 11-mo-old children. Naive IgD⁺CD27⁻, IgD⁺CD27⁺, and switched IgD⁻CD27⁺ B cells were sorted from the blood samples of donors 1 and 2. Total RNA from each cell fraction was reverse transcribed and V_H6 or V_H3.15 μ or γ transcripts were amplified by PCR, using a seminested strategy (see Materials and methods). The PCR products were labeled by a run-off reaction with specific fluorescent V_H-FR3 primers, and subjected to electrophoresis on an automated sequencer. The resulting size distribution of the peaks directly reflects the size distribution of H-CDR3 for the given transcripts. Peaks identified by an asterisk were further sequenced to evaluate intrapeak clonal diversity.