precipitophore

pre·cip·i·to·phore

(prē-sip'i-tō-fōr'),
In Ehrlich side-chain theory, the portion of a precipitin molecule that is required in the formation of a precipitate, as distinguished from the haptophore group.
[precipitin + G. phoros, bearing]

precipitophore

(prē-sĭp′ĭt-ō-for″)
The part of a precipitin that produces the actual precipitation.