Clonality pattern of immunoglobulin gene rearrangements, analyzed by PCR. (A) DNA was extracted from samples, and 2 PCRs were performed using 2 sets of primers (FR3/JH and FR2/JH) to amplify all the size-variable CDR3 rearranged regions (FR2, GC(C/T) (C/T)CC GG(A/G) AA(A/G) (A/G)GT CTG GAG TGG; FR3, ACA CGG C(C/T)(G/C) TGT ATT ACT GT; JH, ACCTGAGGAGACGGTGACC). (B-E) PCR products were loaded on an ABI prism fragment size gel analysis. Four patterns were observed; when a polyclonal B-cell population was present in the sample, random sizes of all CDR3 regions resulted in a gaussian distribution of peak sizes (B). Several peaks could dominate in a sample without individualization of one peak, reflecting an oligoclonal pattern (C). One peak could be clearly individualized, either with a strongly dominant pattern, ie, with a low polyclonal background (D) or as a weak dominant peak, that is, with an intense polyclonal background (E). Patterns such as those in panels B and C were considered nonclonal. When a pattern such as that in panel D or E was observed either from FR3/JH or FR2/JH PCR, the sample was considered clonal.