Peptide-protein conjugates are used in order to generate specific antibodies against peptide sequences.
Typically, individual peptide sequences are too small to trigger an adequate immune response. Therefore, they are linked covalently to bigger and more complex molecules (normally proteins), so that they show immunogenetic characteristics.
The epitopes contained in the carrier proteins, such as KLH (keyhole limpet hemocyanin), BSA (bovine serum albumin) and OVA (ovalbumin), stimulate the T helper cells. This supports triggering of an immune response of the B cells, inducing the biosynthesis of sequence-specific antibodies.
Since the immune system reacts to epitopes of the carrier protein as a whole, antibodies are generated against the carrier protein as well as against the peptide sequence.