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Abstract In mammals, T cell migration is under circadian control, likely to anticipate daily rhythms in infection risk. Glucocorticoids control this process, and malnutrition is associated with increased glucocorticoid levels. Therefore, we evaluated whether malnutrition disrupts the circadian migratory patterns of T cells. Malnutrition did not impact circadian patterns of T cell residency of lymphoid tissues; indicating that fluctuations, rather than specific concentrations, of glucocorticoids are a key circadian signal. Additionally, the total number of CD4+ and CD8+ T cells in the lymph nodes and blood were lower in malnourished as compared to well-nourished mice. However, the percentage and total number of naïve T cells was maintained in the lymph nodes, blood, and spleen of malnourished mice, suggesting preferential preservation of naïve T cells. Interestingly, the percentage and total number of CD4+ and CD8+ T cells in the bone marrow was elevated significantly in mice on a malnourished diet. Additionally, malnourished CD4+ and CD8+ T cells in the bone marrow showed significantly high CCR7 expression and CCL21 expression was increased in malnourished bone marrow compared to control. CCR7 and its chemokine, CCL21, may be responsible for trafficking malnourished T cells to the bone marrow during malnutrition. Overall, these findings suggest that the bone marrow may contribute to naïve T cell preservation during malnutrition. NSF-MRI [DBI- 1920116] NSF -RUI [IOS-1951881] 

Abstract Glucocorticoids contribute to the daily migration patterns of T cells in well-nourished organisms and are elevated in the malnourished. We examined the effect of malnutrition on T cell migration by comparing the migration patterns of adoptively transferred malnourished and control T cells in the lymphoid organs of malnourished and control recipients. We found that malnourished T cells generally entered lymphoid tissues more efficiently than control T cells, regardless of recipient. Strikingly, the bone marrow of malnourished recipients attracted naïve malnourished T cells, but not control T cells, more efficiently than control bone marrow. In contrast, the spleens of malnourished and control mice attracted similar numbers of naïve T cells. Further experiments revealed that T cells residing in the bone marrow of malnourished mice express higher levels of CCR7 and lower levels of CD11a than control T cells. We also examined the effect of T cell-specific deficiency of the glucocorticoid receptor on T cell migration to the bone marrow in malnourished mice. Indeed, similarly low percentages of glucocorticoid receptor deficient T cells were observed in the bone marrow of malnourished and control mice, indicating that T cell expression of the glucocorticoid receptor is required for T cell migration to the bone marrow. Overall, we have determined that malnutrition modifies both the bone marrow and naïve T cells to promote naïve T cell migration to the bone marrow and that at least the T cell-specific effects are mediated via the glucocorticoid receptor. NSF-MRI [DBI- 1920116] NSF-RUI [IOS-1951881]