Pyrocyte
A pyrocyte was a type of  that occurred naturally in Ferengi and Kazon blood. 

Ferengi pyrocytes provoked an extreme allergic reaction when introduced through the skin to a Human.

In 2366, Arridor distilled pyrocytes from DaiMon Goss and used them to sicken Mendoza, the negotiator representing the Federation in discussions over the rights to the Barzan wormhole. ()

Pyrocytes were an integral part of Kazon blood. When an injured Kazon was beamed aboard the  in 2371, The Doctor discovered that his blood cells had bonded with metallic matter, due to tampering with Federation replicator technology. The Doctor had to completely replace the pyrocytes of the Kazon and did a cytological screening of the Voyager crew, looking for a donor. ()

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fr:Pyrocyte
Anatomy
Microorganisms