Aging impacts isolated lymphoid follicle development and function

We observed that aged mice have increased numbers of ILFs and increased numbers of structures corresponding to an early stage of CPs transforming into ILFs. The cellular composition of ILFs in aged mice is altered with a smaller B-lymphocyte population and an increased T-lymphocyte population. The ILF T-lymphocyte population is notable by the presence of CD4+ CD8αα+ T-lymphocytes, which are absent from the systemic compartment. The smaller B-lymphocyte population in ILFs from aged mice is directly correlated with decreased mRNA and protein expression of CCL20 and CXCL13, two chemokines that play crucial roles in recruiting B-lymphocytes into ILFs. Aged mice had elevated levels of serum and fecal immunoglobulins and despite the decreased B-lymphocyte population, ILFs from aged mice displayed increased IgA production. The immunoglobulin repertoire was skewed in aged mice, and ILFs demonstrated a repertoire usage similar to that of the systemic pool in both young and aged mice.Here we observed that ILF development, cellular composition, and immunoglobulin production are altered with aging suggesting that ILF dysfunction contributes to mucosal immunosenescence.Immunosenescence is the age-related decline and dysfunction in protective immunity with serious clinical consequences [1-4]. With aging, bacterial and viral infections in the lungs, skin, and urinary tract become more common [5-7]. Compounding this susceptibility to infection, the rates of seroconversion after prophylactic vaccination decrease proportionally with advancing age [8,9]. Related to the decreased ability to mount effective immune responses to pathogens, immunosenescence also leads to a decline in effective immune surveillance potentiating an increased incidence of malignancy [10]. Finally, immunosenescence is not only associated with declining host immune competence, but also with immune dysregulation manifested by an increased incidence in autoimmune and chronic inflammatory disorders with increasing