The switch region and {HEAD ~ membrane exons} of the invention may comprise {TAIL ~ a human gamma 2 constant region} and the secreted constant region exons are from a human gamma 1 or a human gamma 4 constant region 
comprise
The switch region and { HEAD ~ membrane exons } of the invention may comprise { TAIL ~ a human gamma 2 constant region } and the secreted constant region exons are from a human gamma 1 or a human gamma 4 constant region
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH