Final answer:
Superantigens are the type of toxin most likely to elicit pyrogenic effects, causing fever and a severe immune response through the release of excessive cytokines.
Step-by-step explanation:
The type of toxin most likely to have pyrogenic effects in human hosts is the superantigen. Superantigens, like those produced by Staphylococcus aureus (responsible for toxic shock syndrome) and Streptococcus pyogenes, cause a potent immune response by nonspecifically activating a large number of immune cells. This activation leads to the excessive release of cytokines, which can result in fever (pyrogenic effect), as well as other severe symptoms such as low blood pressure, shock, and multi-organ failure.
Compared to other toxins like A-B toxins and endotoxins, superantigens are distinguished by their mechanism of causing widespread immune activation rather than targeting specific cellular processes. Smith and Hawkins (1990) confirmed exotoxins, including superantigens, are harmful to humans, and recent research emphasizes the role of cytokines like TNFa and IFNy in the host's immune response to such infections.