Phytohaemagglutinin skin-swelling test in scarlet rosefinch males: low-quality birds respond more strongly
Abstract
The phytohaemagglutinin (PHA) skin-swelling test is one of the most widely used methods for cell-mediated immunity measurement in immunoecology. Here we examined the linkage between several condition-dependent traits, including the red ornamental coloration of the plumage, and the magnitude of the PHA-induced immune response in scarlet rosefinch, Carpodacus erythrinus, males.
Histological analysis showed that the swelling response was dependent on basophil activity. The magnitude of the response was associated with individual size, carotenoid-based ornamental coloration and a ptilochronological marker of feather growth at the time of moulting.
As the magnitude of the response was related negatively to ornament saturation and positively to ornament lightness, our results indicate stronger responsiveness in inferior males. Highly ornamented, healthier individuals recruited fewer basophils into the inflamed tissue causing less intense swelling.