Immunoglobulin heavy and light chain gene sequences of a human CD5 positive immunocytoma and sequences of four novel VHIII germline genes.

To analyse the V genes expressed by an IgM lambda CD5-positive immunocytoma heavy and light chain V region genes were cloned and sequenced. The heavy chain is composed of a previously undescribed VHIII gene joined to an unknown D gene and to JH4. The light chain V region is composed of a V lambda II gene rearranged to J lambda 1. In an attempt to clone the germline counterpart of the VHIII gene expressed in the immunocytoma PCR amplifications of genomic DNA were carried out and four previously unknown VHIII genes were identified. As several independent clones for the heavy and light chain V region genes were sequenced the rate of somatic mutation of the V genes was calculated to be below 2 x 10(-5)/bp/cell division.