Lox recombination is used to increase library diversity by shuffling all VH genes with all possible VL genes in a multi step process. In the figure below, vector maps are shown indicating the antibody variable regions (VH and VL), the lox recombination sites (pink and blue boxes, connected by lines), as well as other plasmid elements. The introduction of two different scFvs by infection into a bacterium in which Cre recombinase is expressed, results in the generation of four scFvs: the two original (VLA-VHA and VLB-VHB) and two new ones VLA-VHB and VLB-VHA) arising from the recombination of the two VH and VL genes.
As up to twenty different scFvs are able to enter a single bacterium, up to four hundred different antibodies can be created by a single bacterium.
This increase in diversity results in the ability to select antibodies of higher affinity, by virtue of sampling more "sequence space".