Detecting molecules

A molecule of interest, such as a target molecule, and particularly those molecules that have a low relative abundance in a test sample, can be identified or detected by depleting molecules from the test sample that have a higher relative abundance than the target molecule. The increase in the relative abundance of the target molecule is achieved by using the test sample as an immunogen to produce antibodies that are then used to deplete molecules having a higher relative abundance than the target molecule from the test sample. The production of antibodies by immunising with the test sample is particularly advantageous because in the subsequent depletion step, it is possible to deplete molecules having a higher relative abundance from the sample without knowing the identity of these molecules. There is no need for knowledge of the molecules having a higher relative abundance in the test sample in order to deplete these from the sample. Thus a target molecule comprised in an otherwise poorly characterised test sample can be detected by the process.