Protein expression refers to the way in which proteins are synthesized, modified and regulated in living organisms. In protein research, the term can apply to either the object of study or the laboratory techniques required to manufacture proteins. This article focuses on the latter meaning of protein expression. ackground. Gene expression profiling of RNA extracted from peripheral blood is an informative method used to identify biomarkers, examine disease states, and investigate immune responses. ... Common laboratory practice often includes fractionation of whole blood components prior to RNA extraction. Transcription profiling. This is one of the most popular study types, also known as 'expression profiling'. It involves the quantification of gene expression of many genes in cells or tissue samples at the transcription (RNA) level.