Considering evolved heat tolerance helps predict the immunological consequences of climate change.

Among the most damaging anticipated consequences of climate change are rising global temperatures that are expected to exceed the heat tolerance of many species worldwide. Species' heat tolerance reflects adaptation to their historical environments, and rapid increases in ambient temperatures create a mismatch between evolved thermal tolerance and present-day heat exposures. This mismatch has severe implications because high temperatures can disrupt physiological processes across levels of biological organization. The immune system, specifically, may be particularly susceptible to dysregulation under climate warming because it is highly responsive to temperature. Although a rich body of empirical and clinical research has characterized the effects of heat on immunity, these findings are rarely interpreted in the context of evolved heat tolerance. Here, we provide a framework for predicting the immunological consequences of climate change by integrating results derived from five decades of immune research with evolutionary principles of heat tolerance. This framework offers a strong foundation for predicting the health and disease consequences of immune vulnerability to heat in a rapidly warming world.