B-cell clones with an identical V3-15 CDR3 shared by IgM⁺IgD⁺CD27⁺ B cells from blood and spleen during a T-independent response. Amplification of V3-15–C_μ mRNA sequences was performed from naive and IgM⁺IgD⁺CD27⁺ B cells of a 9-year-old child undergoing splenectomy and immunized against S pneumoniae and N meningitidis (plain polysaccharidic vaccines). The following samples were analyzed: blood before immunization, blood at the time of splenectomy (ie, 8 days after immunization), spleen, and blood 5 weeks after immunization. The first V3-15–specific PCR products were further amplified with V3-15–specific FR3 and C_μ primers, and the resulting products fractionated by denaturing gel electrophoresis. A specific CDR3 size was excised from the gel after silver staining and reamplified with the same FR3 and C_μ primers, and sequences were determined after cloning. Several PCR amplifications were performed from 2 independent cDNAs for each cell sample. The recurrent CDR3s encompassing the V3-15 and J_H3 junctions observed in the various IgM⁺IgD⁺CD27⁺ fractions are shown, with the most frequently occurring sequence taken as reference (CDR3 is defined as amino acids included between the conserved Cys residue of FR3 and Trp residue of J_H segments). ^*Clones found repeatedly in independent PCR amplifications.