{TAIL ~ The human immunoglobulin heavy chain transgene} in the foregoing animals comprises a human constant region gene segment comprising exons encoding {HEAD ~ the desired heavy chain isotype}, operably linked to switch segments from a constant region of a different heavy chain isotype, i.e., a non cognate switch region 
{ TAIL ~ The human immunoglobulin heavy chain transgene } in the foregoing animals comprises a human constant region gene segment comprising exons encoding { HEAD ~ the desired heavy chain isotype } , operably linked to switch segments from a constant region of a different heavy chain isotype , i.e. , a non cognate switch region
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH