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