Genetically modified T cell receptor mice

A method for obtaining a nucleic acid sequence encoding a human T Cell Receptor (TCR) variable domain from a genetically modified mouse, the method comprising

• (a) immunizing a genetically modified mouse with an antigen,
• wherein the genome of the genetically modified mouse comprises:
• (i) a humanized TCR α gene comprising a replacement of endogenous TCR variable (V) α and endogenous TCR joining (J) α gene segments with unrearranged human TCR Vα and unrearranged human TCR Jα gene segments,
• wherein the unrearranged human TCR Vα and unrearranged human TCR Jα gene segments are operably linked to a mouse TCR constant (C) a gene sequence, and
• (ii) a humanized TCR β gene comprising a replacement of endogenous TCR Vβ, endogenous TCR diversity (D) β, and endogenous TCR Jβ gene segments with unrearranged human TCR Vβ, unrearranged human TCR Dβ, and unrearranged human TCR Jβ gene segments,
• wherein the unrearranged human TCR Vβ, unrearranged human TCR Dβ, and unrearranged human TCR Jβ gene segments are operably linked to a mouse TCR Cβ gene sequence;
• (b) allowing the genetically modified mouse to express a chimeric TCR that binds the antigen,
• wherein the chimeric TCR comprises a chimeric TCR α polypeptide and a chimeric TCR β polypeptide,
• wherein the chimeric TCR α polypeptide comprises a human TCR α variable domain operably linked to a mouse TCR Cα domain, and
• wherein the chimeric TCR β polypeptide comprises a human TCR β variable domain operably linked to a mouse TCR Cβ domain;
• and
• (c) obtaining a nucleic acid sequence encoding a human TCR variable domain from the genetically modified mouse that expresses the chimeric TCR.