This figure illustrates the immunofixation pattern of a single serum specimen with antisera to heavy chain determinants of IgA, IgG, and IgM, and to kappa and lambda light chain determinants. It shows a discrete IgG band (seen as a dark band) and a discrete lambda band with similar mobility, indicative of the presence of an IgG lambda monoclonal protein. There is also an IgM kappa monoclonal protein.