Depletion of the High-abundance Plasma Proteins

Body fluids, like plasma and urine, are comparatively easy to obtain and are useful for the detection of novel diagnostic markers by applying new technologies, like proteomics. However, in plasma, several high-abundance proteins are dominant and repress the signals of the lower-abundance proteins, which then become undetectable either by two-dimensional gels or chromatography. Therefore, depletion of the abundant proteins is a prerequisite for the detection of the low-abundance components. We applied affinity chromatography on blue matrix and Protein G and removed the most abundant human plasma proteins, albumin and the immunoglobulin chains. The plasma proteins, prior to albumin and immunoglobulin depletion, as well the eluates from the two chromatography steps were analyzed by two-dimensional electrophoresis and the proteins were identified by MALDI-TOF-MS. The analysis resulted in the identification of 83 different gene products in the untreated plasma. Removal of the high-abundance proteins resulted in the visualization of new protein signals. In the eluate of the two affinity steps, mostly albumin and immunoglobulin spots were detected but also spots representing several other abundant plasma proteins. The methodology is easy to perform and is useful as a first step in the detection of diagnostic markers in body fluids by applying proteomics technologies.