2Aindicated they were generally as abundant as AZGP1, PEBP1, REL and THBS4
2Aindicated they were generally as abundant as AZGP1, PEBP1, REL and THBS4. By definition, autoantibodies are present in autoimmune diseases but they have also occasionally been found to be associated with other diseases including cancers.1Autoantigens could trigger an immune response because they are over/aberrantly expressed, are mislocalized, have point mutations,2have altered post-translational modifications (PTMs),3are misfolded, or are truncated due to aberrant splicing or proteolytic cleavage.4However, it is still not well known why certain proteins become autoantigens or why some individuals make autoantibodies and others do not. Furthermore, we have no idea how prevalent autoantibodies are in healthy individuals. Autoantibodies are attractive sources of potential disease biomarkers.5Immune surveillance often occurs early during a disease process so antibodies could potentially detect a disease before overt symptoms occur particularly in chronic diseases. Antibody production can be amplified as part of an immune response, so low levels of antigen can still lead to a robust signal. Antibodies are high affinity, structurally stable reagents, reducing the need for extensive upfront purification. Thus, if immune complexes are identified that are specific to disease conditions, definitive clinical screening might be possible. In fact, there are a several assays for antigen-antibody or circulating immune complexes (CIC) currently used in the clinic. Most of these assays have been developed for bacterial, viral or allergen antigens. In a few cases, detection of autoantigens as CIC has been proposed to enhance the sensitivity of cancer detection or prognosis monitoring utilizing prostate-specific antigen (PSA),6squamous cell carcinoma antigen,7carcinoembryonic antigen8and CA-125.9Thus, autoantigen-antibody complexes have been shown to be useful disease biomarkers, but progress in the discovery of new CICs has been extremely slow. The few current CIC assays that exist were developed based on known protein markers on a Propineb one-at-a-time basis. We believe the major impediment to more broad adoption of CIC as biomarkers is a lack of research tools to screen putative CIC in a high-throughput manner. In contrast to CIC-related methods, there are several screening technologies for free autoantibody detection including protein or peptide arrays,1014reverse capture arrays,15,16and SEREX (serological analysis of tumor antigens by recombinant cDNA expression cloning).1720Protein array analysis to detect autoantigens is usually performed by printing synthetic, recombinant or natural proteins on an array surface followed by incubation with an antibody containing solution and detection of the antibody. Although high density protein arrays are commercially available now, they are costly and if bacterially produced proteins or synthetic peptides are used, it is uncertain that the printed proteins have relevant PTMs. An Propineb alternative method is nucleic acid programmable protein array (NAPPA) where an immobilized DNA template for a tagged version of the protein is translated using reticulocyte lysate and the resulting protein immobilized via an anti-tag antibody within the same spot.21Reverse capture microarrays are another approach that usually involves fractionation of proteins from tissue lysates, cell culture, serum or plasma and spotting the fractions on a microarray. The solution containing the antibody is then incubated on the array and the antibody detected with labeled secondary anti-human antibody. The positive fractions are analyzed for the corresponding antigen. For SEREX methodology, tumor mRNA Propineb is typically converted to cDNA clones, expressed inEscherichia coliand antibodies detected via a variety of screening strategies. All of these methods require that the autoantibody antigen binding site to be available for binding, i.e., not to be complexed with their antigen. In this paper, we propose a novel, high dimensional method to detect antibodies that are complexed WISP1 with their natural autoantigens. Our protocol utilizes a high-density antibody microarray platform that we print in-house. In the examples.