Attrition of T Cell Zone Fibroblastic Reticular Cell Number and Function in Aged Spleens

Aging has a profound impact on multiple facets of the immune system, culminating in aberrant functionality. The architectural disorganization of splenic white pulp is a hallmark of the aging spleen, yet the factors underlying these structural changes are unclear. Fibroblastic reticular cells comprise one stromal cell subset in the spleen that is important for maintenance of architectural organization, yet it remains to be determined how aging impacts these cells. In this study, we sought to determine how aging impacts splenic T cell zone reticular cell (TRC) numbers, morphology, and function. Using a mouse model of aging, we found that aged naive spleens have fewer TRCs than young spleens. This reduction in TRC number correlated with reduced CCL19 and CCL21 concentrations in aged spleens, which may contribute to impaired homing of T cells. CCL21 in both young and aged spleens localized with TRCs. Aged TRCs extended marginally into B cell follicles and may contribute to the blending of the T cell zone and B cell follicles in aged spleens. The described age-related changes in TRCs number and function may be an underlying factor contributing to impaired immune system function with age.