The impact of growth hormone (GH) on immunosenescence: exploring the role of B and T cells

PURPOSE: Immunosenescence is a gradual decline in immune function, leading to increased susceptibility to infections and autoimmune conditions. Growth hormone (GH) has been shown to have an effect on both immune function and aging. In fact, the absence of GH-induced intracellular signaling can slow the aging process, as demonstrated by the longest-lived laboratory mouse (GH receptor gene disrupted or GHR-/- mice). Because GH receptors (GHR) are expressed in B and T cells, and these cells undergo age-related changes that impact immune function, we hypothesized that decreased GH action protects from immunosenescence. To validate this hypothesis, this study aimed to characterize differences in B cell and T cell populations within the lymphoid organs of aged female GHR-/- mice (24 months of age) compared to wild-type controls. METHODS: B and T cell populations in mouse blood, spleen, thymus, and bone marrow (BM) were analyzed by multicolor flow cytometry. RESULTS: The current study showed significantly higher levels of anti-inflammatory follicular (FO) B cells in spleens and BM and lower levels of pro-inflammatory aging-associated B cells (ABC) in the spleens, BM, and blood of aged GHR-/- mice compared to WT mice. In addition, T cell populations in aged GHR-/- mice showed higher levels of naïve T cells and lower levels of memory T cells in the thymus, BM, spleen, and blood. CONCLUSION: Female GHR-/- mice are protected from age-related shifts in lymphocyte populations, suggesting that the absence of GH action mitigates immunosenescence. These results offer novel insights into mechanisms and therapeutic strategies to preserve immune balance and combat age-related immune dysfunction.