Identification of a third type of lambda light chain in mouse immunoglobulins

A third type of mouse lambda chain was identified in the course of examining light chains from four myeloma proteins and two monoclonal antibodies. On the basis of their antigenic properties and a characteristic COOH-terminal tryptic peptide, the light chains from these immunoglobulins had previously been provisionally identified as lambda 2 chains. However, four of these chains, designated now as lambda 3 (or lambda III), were found to share constant region features that clearly distinguish them from the other types of mouse lambda chains (lambda 1 and lambda 2). The amino acid sequence of more than 90% of the lambda 3 constant region (from position 120 to the COOH-terminus) was determined. In this region the lambda 3 sequence differs from the lambda 2 constant region at 5 positions and from the lambda 1 constant region at about 30 positions.