Meeting Abstract
It remains largely unknown how selection from novel pathogens influences host immune phenotypes more broadly, such as immune responses to unrelated pathogens and antigens. In 1994, the bacterial pathogen Mycoplasma gallisepticum (MG) jumped from poultry into house finches in Virginia, causing severe conjunctivitis and reducing survival. MG then spread across the continental United States, causing strong selection on host populations and creating a geographical timeline of host co-evolutionary history with the pathogen. In populations with longer histories of MG endemism, hosts have evolved tolerance to MG, and past work suggests that reductions in pro-inflammatory immune responses are associated with this tolerance. However, it remains unknown whether these immunological changes are limited to MG-specific defenses or whether broader immune responses differ between more- and less-tolerant populations. To examine potential broader effects of MG tolerance, we used four immune antigens to challenge house finches from four populations, ranging from no history of MG endemism to 20+ years of MG endemism. When challenged with phytohemagglutinin, populations differed significantly in the strength of wing web swelling, with populations with longer MG exposure (and thus the highest MG tolerance) on average exhibiting the weakest swelling response. However, population differences were absent for responses to three other antigens (LPS, FSL-1, sheep erythrocytes). These results suggest that the evolution of MG tolerance may have downstream consequences for responses to some antigens, with the potential to influence a host’s ability to respond to novel pathogen challenges, but many components of the host immune system remain unaffected.
