A single rearrangement event generates most of the chicken immunoglobulin light chain diversity.

The chicken immunoglobulin lambda locus contains a single C lambda gene with a unique J lambda element, 1.9 kb upstream. The same V lambda gene (V lambda 1) is rearranged in most cells of the Bursa of Fabricius. This V lambda 1 gene is located, in germ-line configuration, 1.7 kb upstream from J lambda and in the same transcriptional orientation. Eight to twelve variable genes of the same set are found adjacent to the V lambda 1 gene, indicating that V-gene amplification did occur. Three of these genes were sequenced and proved to be pseudogenes, one of them having an inverted polarity. Data suggesting extensive somatic diversification of the V lambda 1 sequence are reported, including the possible use of nonfunctional V elements in a somatic gene-conversion-like process.