Multiple thymi and no thymic involution in naked mole rats?

Excerpt

The naked mole rat (NMR) is a social mammal remarkable for any number of characteristics, most fascinatingly its extreme longevity. Little is known about its immune system, although as a subterranean animal immunity against infectious disease would be expected to be less important than in surface-dwelling social animals. Nonetheless, it provides an intriguing model for interactions of immune ageing with organismal ageing, which is likely to be of great importance, at least in mice [1]. Age-associated changes to the bone marrow niche and hematopoietic stem cells affect the production of T cell progenitors in mice in a dramatic manner [2], but the universal mammalian phenomenon of progressive thymic involution further decreases the capacity of the individual to generate new naïve T cells at older ages. Hence there has been a great deal of interest in preventing or reversing thymic involution in order to maintain diversity of the naïve TCR repertoire, required for the recognition of novel pathogens and cancer antigens. Thus, the hypothesis that such “thymic rejuvenation” would therefore benefit older adults has gained much traction over the years. The corollary to this hypothesis is that species or individuals within species that retain more and better thymic function into later life will be less likely to become “immunosenescent”, which would otherwise have negative consequences particularly for defence against pathogens to which they were not previously exposed. …