Protein arrays are a well-established proteomic tool for the simultaneous analysis of thousands of interaction partners, generally manufactured in an microarray format through immobilization of purified proteins on chemically modified microscope slides . An alternative to the microarray format are protein macroarrays produced by printing of annotated libraries of E.coli clones, expressing recombinant human protein, on large 22×22cm polyvinylidene fluoride (PVDF) membranes . Since their introduction in the early 2000' the protein macroarrays have been frequently used with around 100 published studies in a wide range of applications from proteinprotein , peptide-protein , enzyme-substrate and posttranslational modification interaction studies , to antibody specificity validation , antibody target discovery , antibody isotyping and clinical autoantibody screening . The extensive usage of the protein microarrays can be attributed to two innate characteristics unique to the platform: i) E.coli expression clones are spotted directly on PVDF membranes, ensuring consistent protein concentrations intrinsic to each individual expression clone, thereby avoiding the need for cumbersome large-scale protein purification and characterisation procedures essential for the generation of most protein microarray formats; and ii) each individual colony spot on the macroarray comprises of a single recombinant human protein and a collection of all E.coli proteins, thereby providing a natural blocking background consistent across the entire array and hence ensuring excellent experimental signal to noise ratios .