Braude has published his new testosterone immunoredistribution hypothesis in the journal Behavioral Ecology. He specifically analyzed three studies that tried to link testosterone and immunosuppression and countered them with the redistribution hypothesis. He also cited recent literature indicating an association between testosterone and a healthy immune system in lizards, fowl and voles. To understand why evolutionary biologists look at animals and sexual display, it's important to realize that, before the days of the Hefner lifestyle, courtship and breeding were very stressful. They still are for male birds and mammals, which have higher levels of testosterone during breeding season, in part because of the thrill of the hunt but also because males have to fight other males to gain the favor of their preferred females.
Males get more wounds during breeding season than at any other time of the year.
Braude and others think the high testosterone levels during breeding season could serve to prime the animals' immune systems to defend against wounds. I think the old theory about immunosuppression made a lot of sense on the surface. You can see it every day. If someone's stressed, they're likely to get sick. The simple interpretation is that the immune system is suppressed.