Molecular mechanisms and selection influence the generation of the human V lambda J lambda repertoire.

To define the lambda light chain repertoire in humans, a single-cell PCR technique using genomic DNA obtained from individual peripheral B cells was employed. Of the 30 known functional V lambda genes, 23 were detected in either the nonproductive or productive repertoires. Specific V lambda genes, including 2A2, 2B2, 1G, and 4B, were overexpressed in the nonproductive repertoire, whereas some V lambda genes, such as 3R, 2A2, 2B2, 1C, 1G, and 1B, were overexpressed in the productive repertoire. Comparison of the nonproductive and productive repertoires indicated that no V lambda genes were positively selected, whereas a number of V lambda genes, including 4C, 1G, 5B, and 4B, were negatively regulated. All four of the functional J lambda segments were found in both repertoires, with J lambda 7 observed most often. Evidence of terminal deoxynucleotidyltransferase activity was noted in nearly 80% of nonproductive V lambda J lambda rearrangements, and exonuclease activity was apparent in the majority. Despite this, the mean CDR3 length was 30 base pairs in both productive and nonproductive repertoires, suggesting that it was tightly regulated at the molecular level. These results have provided new insights into the dimensions of the human V lambda repertoire and the influences that shape it.