If a B cell contains two mu chains and two lambda chains and is self reactive can it go back and rearrange its kappa light chains? I'm not sure if it can only try to rearrange its lambda light chains or if it can go back and try to rearrange kappa chains as well. Background info: the light chain is the smaller of the two types of polypeptide chain in an immunoglobulin molecule. There are two classes of light chain known as the kappa and lambda light chains. During B-cell development the light chain genes rearrange. First one kappa gene is rearranged; if this doesn't produce a functional protein then the kappa gene on the second chromosome is rearranged; if a functional protein is still not produced then the lambda gene is rearranged one chromosome at a time until a successful rearrangement is produced.