providing a retainer with a plurality of compartments, wherein a first compartment comprises a first antibody and {HEAD ~ a second compartment} comprises {TAIL ~ a second antibody} 
providing a retainer with a plurality of compartments , wherein a first compartment comprises a first antibody and { HEAD ~ a second compartment } comprises { TAIL ~ a second antibody }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL