a. Checking an anti-free lambda light chain antiserum in IF: a procedure using a serum containing a monoclonal IgGlambda + free lambda light chains. A standard IF of this serum, performed with anti-bound and free light chain antisera, showing two distinct bands with the anti-lambda antiserum, identifies both a complete monoclonal IgG and free lambda light chains. T is the serum electrophoresis; G stands for anti-IgG reaction; A for anti-IgA reaction; M for anti-IgM reaction; k means anti-bound and free kappa reaction; l for anti-bound and free lambda reaction
b. Free l stands for antiserum having the proper specificity, thus exhibiting a single band, for the free lambda light chains, without any cross-reaction with complete IgG lambda bound light chains.
c. Free k stands for a correct anti-free kappa light chain antiserum, as these antisera are usually tested as pairs, kappa and lambda from the same manufacturer. Tested free (?) l is for an antiserum having an improper specificity for identifying free light chains, since it provides two bands, one for free lambda light chains and a second one for IgG bound light chains: it is a bispecific antiserum, revealing both bound and free lambda light chains.