The mysterious immunoglobulin light chain

The immunoglobulin light chain is mysterious from different points of view. In an evolutionary perspective there seems to be at least three major pathways but it is today impossible to say which of them is the most ancient one and which isotype belongs to which branch. It is also difficult to assess the contribution of the light chain to the binding capacity of the antibodies. It is possible that it differs from antibody to antibody but the fact that there are antibodies in camels and sharks without any light chain suggests that it is perhaps not necessary for good antigen binding.