Recombinant full-length single chain immunoglobulins

A recombinant nucleic acid molecule comprising:

• a sequence encoding an immunoglobulin heavy chain variable region (VH),
• a sequence encoding an immunoglobulin light chain variable region (VL),
• a sequence encoding a light chain constant region (CL),
• two sequences encoding peptide linkers (PL1 and PL2), wherein the peptide linkers PL1 and PL2 comprise SEQ ID NOs:
• 1, 3, 4, 5, 6, or 7;
• a donor splice site, wherein the donor splice site is a donor splice site for junction with a CH1 domain of constant immunoglobulin heavy genes, and
• wherein the nucleic acid encodes a molecule comprising the following structure:
• VH-PL1-VL-CL-PL2-donor splice site,
• wherein PL1 and PL2 are identical or different, and
• wherein the nucleic acid molecule is integrated between the joining region (JH) genes and the constant region (CH) genes of immunoglobulin heavy chains in the genome of a host cell, wherein the host cell is a mouse B cell or a human B cell, thereby encoding a full-length single chain immunoglobulin comprising VH-PL1-VL-CL-PL2-CH wherein VH-PL1-CL-PL2 are encoded by the recombinant nucleic acid molecule and CH is encoded by the host cell genome.