Immunological distinction between piscine and mammalian metallothioneins.

1. Separate antisera to metallothioneins (MT) from rainbow trout and horse were produced in mice and their reactivity with the respective immunogen was confirmed using an ELISA. 2. The ELISA, used in a competitive mode, revealed that the anti-horse MT serum did not cross-react with trout MT. Reciprocally, the anti-trout MT serum did not show any reactivity with horse MT. 3. The anti-rainbow trout MT serum was shown to cross-react totally with MTs from plaice, flounder, turbot, perch, salmon and pike, but exhibited no reactivity towards MTs from human, mouse, rat, worm or crab. Partial reactivity with the proteins isolated from oyster and mussel was demonstrated. 4. The anti-horse MT serum cross-reacted totally with MTs from human, rat and rabbit but no reactivity was demonstrable when MT from either plaice or worm was tested. 5. The behaviour of apo-, holo- and recombinant rainbow trout MTs, in which the metal content was different, indicated that reactivity with anti-MT antibodies was not dependent on the presence or nature of the metals bound in the protein. 6. The patterns of reactivities were analysed in relation to the known amino acid sequences of MT.