The major difference between kappa and lambda genes is that rather than a single C k region as found with kappa, the lambda gene contains six C l regions each associated with a particular J k region. Again, rearrangement of the DNA places a single V l segment directly adjacent to one of six J l segments. During transcription, any intervening sequences are removed by RNA splicing, following which the messenger RNA is translated into a completed lambda light chain protein. If k rearrangement fails and a successful l rearrangement takes place, the k genes are either aberrantly rearranged or deleted entirely. As with failure of heavy chain recombination, if all k and l attempts at recombination fail, the cell is thought to die.
Light chain allelic exclusion allows a B lymphocyte to make only one type of antibody.
At first B cells produce an immunoglobulin with a heavy chain of either the m or in some instances m and d . Thus effect or function varies, but with the same antibody specificity. See B cell maturation. The B lymphocyte gene rearrangements are the means by which B cells respond to untold numbers of antigens, producing millions of different B cell clones. The molecular genetics of B lymphocytes is linked to B cell growth, differentiation, and response including immumoglobulin production.