Broad and Largely Concordant Molecular Changes Characterize Tolerogenic and Immunogenic Dendritic Cell Maturation in Thymus and Periphery

Dendritic cells (DCs) are instrumental in the initiation of T cell responses, but how thymic and peripheral tolerogenic DCs differ globally from Toll-like receptor (TLR)-induced immunogenic DCs remains unclear. Here, we show that thymic XCR1(+) DCs undergo a high rate of maturation, accompanied by profound gene-expression changes that are essential for central tolerance and also happen in germ-free mice. Those changes largely overlap those occurring during tolerogenic and, more unexpectedly, TLR-induced maturation of peripheral XCR1(+) DCs, arguing against the commonly held view that tolerogenic DCs undergo incomplete maturation. Interferon-stimulated gene (ISG) expression was among the few discriminators of immunogenic and tolerogenic XCR1(+) DCs. Tolerogenic XCR1(+) thymic DCs were, however, unique in expressing ISGs known to restrain virus replication. Therefore, a broad functional convergence characterizes tolerogenic and immunogenic XCR1(+) DC maturation in the thymus and periphery, maximizing antigen presentation and signal delivery to developing and to conventional and regulatory mature T cells.

Changes in the histidine residues of Cu/Zn superoxide dismutase during aging

Cu/Zn-Superoxide dismutase activity (Cu/Zn-SOD) was studied in liver from 3- and 24-month-old rat. A significant decrease of enzyme activity in liver of the aged rat was found. Various amino acid residues and protein carbonyl groups (CO) were measured in purified young and old enzyme. It was found that the 'old' enzyme had one histidine fewer and higher CO content than the 'young' Cu/Zn-SOD. Inactivation 'in vitro' of purified commercial bovine erythrocyte Cu/Zn-SOD led to a decrease in the enzymatic activity, an increase in the CO and one histidine residue modified. A similar behavior between aging and oxidation was suggested.