Delving into the innate and adaptive immunity of camelids: a paradigm of interspecies adaptation and evolutionary...

Camelids have evolved to survive some of the most challenging climatic conditions on our planet and are resilient to physiological stress such as temperature extremes, drought, storms, intense ultraviolet radiation, dehydration, and starvation. They exhibit remarkable resistance to several diseases that severely affect other livestock including tetanus, foot-and-mouth disease, and bovine spongiform encephalopathy. The robust nature of the camelid immune system, which maintains functionality under extreme conditions, is remarkable. The special features of the camelid immune system include differences (when compared to ruminants) in the distribution and anatomy of their lymphoid organs. The innate immune system merits further investigation, though potent antimicrobial peptides have been identified in camelid milk. It is in the adaptive immune response that the most distinctive aspects of the camelid immune system are seen, especially, the presence of heavy chain-only antibodies, somatic hypermutation of T cell receptors; in the dromedary, a significant number of γδ T cells. In this review, the interplay between innate and adaptive immunity in camelids is examined, highlighting their functions in systemic and mucosal immune defense. An understanding of these adaptations is important for the development of innovative biomedical applications, such as nanobody-based diagnostics and therapeutics. In addition, dromedary camels are the main likely animal reservoir for the Middle East Respiratory Syndrome Coronavirus (MERS-CoV), an emerging zoonotic pathogen with potential for large-scale human spillover. Finally, as climate change is likely to result in increased environmental stress worldwide, a comparison of how the immune system in different species has adapted to their environment will be important.