Peripheral blood contains a variety of cell types including erythrocytes, granulocytes, lymphocytes, monocytes, natural killer cells and platelets. In PBMCs, several cell types including neutrophils, basophils, eosinophils, platelets, reticulocytes and erythrocytes are depleted. Because each of the contributing cell types expresses a unique gene expression signature relating to its function, the relative proportions of the cell types affect the gene expression profile [6]. In addition, the relative proportions of the cell types can change rapidly following disease-related or inflammatory responses. Clearly, this variability may confound the interpretation of gene expression differences between control and disease groups.
