Dheas Enhances Germinal Center Responses in Old Mice
Antigen (Ag) transport leads to the formation of the Ag retaining FDC-reticulum.1 Studies have demonstrated that in old (23 month) mouse lymph nodes, Ag transport is defective and only a small fraction of the expected Ag transport sites develops.2 The Ag transport sites that develop, form atrophic discontinuous pathways of globular structures. The Ag transport deficit corresponds to a similar deficit in the number of FDC-retaining reticula by day 1–3 after antigenic challenge. Follicular dendritic cells that develop are ultrastructurally atrophic, retain little Ag, and produce no iccosomes. In recent studies, we examined the capacity for germinal center development in old mice with a deficit of FDC Ag-retaining reticula. Germinal center development was monitored by image analysis utilizing the peanut agglutinin (PNA) binding feature of germinal center B cells histochem-ically with PNA-horseradish peroxidase (HRP) conjugates.3 The results showed a marked age-related depression of germinal center development. Interestingly, the ratio of FDC-reticula to germinal center numbers remained 1:1, similarly to that shown for young immune mice.3 These ratios support the concept that germinal center development in immune mice requires Ag-retaining FDC, an observation in complete agreement with the more recent in vitro data.4 Thus the lack of capacity of old mice to produce germinal centers reflects age-related defects associated with antigen transport and FDC development.
KeywordsDepression DMSO Germinal Half Life Androgen
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