Albumin depletion of human plasma also removes low abundance proteins including the cytokines

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Abstract
The use of proteomics for efficient, accurate, and complete analysis of clinical samples poses a variety of technical challenges. The presence of higher abundance proteins in the plasma, such as albumin, may mask the detection of lower abundance proteins such as the cytokines. Methods have been proposed to deplete the sample of these higher abundance proteins to facilitate detection of those with lower abundance. In this study, a commercially available albumin depletion kit was used to determine if removal of albumin would measurably reduce detection of lower abundance cytokine proteins in human plasma. The Montage® Albumin Deplete Kit (Millipore) was used to deplete albumin from LPS‐stimulated whole blood from 15 normal human donors. Albumin depletion was measured using the BCG reagent and SDS‐PAGE, and cytokine recovery was determined by a microassay immunoassay that measures both pro‐ and anti‐inflammatory cytokines. Average albumin depletion from the samples was 72%. However, several cytokines were also significantly reduced when the albumin was removed from the plasma. Additionally, there was a variable reduction in cytokine recovery from a known mixture of cytokines in a minimal amount of plasma that were loaded onto the columns. These data demonstrate that there may be a non‐specific loss of cytokines following albumin depletion, which may confound subsequent proteomic analysis.