Some of {TAIL ~ the first step antibody} binds to antigens present at or near {HEAD ~ the body part}, and unbound first step antibody is washed away 
Some of { TAIL ~ the first step antibody } binds to antigens present at or near { HEAD ~ the body part } , and unbound first step antibody is washed away
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH