What is a phage or bacteriophage?
Phages are viruses that infect bacterial cells. There are several types of phages that have been used as vehicles for phage display including Ff filamentous phage, Lambda and T7. In phage display, the bacteriophages are used to construct different phage libraries as peptide libraries or antibody library
History of phage display
Phage display technology was first introduced in 1985 by George Smith. After that many advantages have been introduced including the way to construct a phage library like antibody library to select phage display antibodies.
Advantages of phage display
Phage display is a system for large scale study and selection of proteins, peptide and antibodies based on their binding affinity and specificity. One advantage of phage display is the enormous diversity of variant proteins that can be represented in a phage library. Phage display provides a means of rapidly screening large numbers of proteins against potential binding partners.

Antibody libraries

Review of antibody libraries

There are several type of antibody libraries based on phage display technology like immunized antibody libraries and naive antibody libraries.

There are several  strategies that can be used to construct  phage display antibody libraries. Commonly  synthetic or semi-synthetic antibody libraries are designed from human variable light (VL) and variable heavy (VH) repertoires. Single human frameworks with diversity are introduced in the the antigen binding site of  VH and VL domains. Another way to construct antibody libraries are amplifying the variable gene repertoires of one or more individuals. Oligonucleotides corresponding to the V gene families are used in the amplification. The antibody libraries are constructed by a random combination of VL and VH chain coding genes. The amplified antibody coding genes are assembled to be displayed on the surface of the phages  as Fab or scFv antibody fragments .In theory, each clone represent a specific antigen-binding site, obtained from the natural repertoire. The panning procedure mimics the B-cell clonal selection system. In the construction of antibody libraries are important to make sure that the antibody libraries have enough diversity since this will be crucial in selecting binding clones for any given antigen.