RESUMEN
A new allelic form of the human IgLC2 gene is described. The marker involves a T to C substitution in the C lambda 2 constant region gene, a silent substitution at amino acid coding position 178 (YAASSYLSL) and two substitutions in the 3'-flanking region. Analysis of IgLC2 alleles in a total of 60 individuals has indicated a frequency of 0.32 for the new allele, which has been designated IgLC2*B2. The *B1 and *B2 alleles encode T and C, respectively, at nucleotide position 212 in the IgLC2 coding region. Both the *B1 and *B2 alleles are found in individuals homozygous for the single-copy RFLP allele of IgLC2/IgLC3 (8 kb EcoRI). Knowledge of alleles of this marker will be important for studies on the expression of the IgLC2 and IgLC3 isotypes in normal and autoimmune lymphocyte populations, as the coding regions of the two isotypes differ only at this position. The marker will also be useful in further studies of linkage with other IgLV and IgLC markers and to establish possible correlations with susceptibility to autoimmune disorders.