A fungus that is killing frogs and other amphibians around the world releases a toxic factor that disables the amphibian immune response. Amphibians have excellent and complex immune systems nearly as complex as humans and they should be able to recognize and clear the fungus. Some frogs produce anti-microbial peptides in the skin that offer a first layer of defense against the fungus. B. dendrobatidis cells and supernatants (the incubation liquid separated from the cells) impaired lymphocyte proliferation and induced cell death of lymphocytes from frogs, mice and humans. The toxic fungal factor also inhibited the growth of cancerous mammalian cell lines. Fungal infection causes rapid behavioral changes frogs become lethargic and start to crawl out of the water suggesting that even though the fungus stays in the skin, the toxic material is having effects elsewhere.