Deterioration of the immune system (immunosenescence) with age is associated with an increased susceptibility to illness autoimmune disease and malignancy and reduced responsiveness to vaccination. alterations in gene manifestation and epigenetic rules occurred already by the age of 4 months compared Ko-143 to one month and persisted in 18-month-old compared to 1-month-old rats. In both organs these changes were accompanied from the modified composition of resident T cell populations. Our study suggests that both senescence and apoptosis may be involved in modified organ function. (Effros 2004 Ko-143 However the molecular mechanisms that underlie those changes are only beginning to become understood. Altered manifestation and activity of several transcription factors are involved in thymic involution (Trebilcock and Ponnappan 1996 Ortman et al. 2002 This suggests that transcriptional profiles in cells of the ageing immune system may be modified. Further senescence plays a role in thymic involution as well as with homeostasis of peripheral T cells. At a molecular level cellular senescence is often linked with the Ko-143 build up of oxidative damage to macromolecules (including DNA as the genetic material and chromatin as the substrate for epigenetic rules). While the build up of mutations has long been hypothesized to be a cause of ageing damage to chromatin has recently been suggested to be involved in aging as well (Sedivy et al. 2008 Consequently we hypothesized that if senescence plays a role in immunosenescence gene manifestation and epigenetic profiles may be vastly modified in main and peripheral immune organs of ageing organisms. To assess this we isolated thymus and spleen cells from 1-month 4 (before or at an early stage of thymic involution) and 18-month-old (at a late stage of thymic involution) male Long Evans rats. Using the Illumina? Gene Manifestation Tgfb3 BeadChip technology we identified transcript levels in total RNA preparations from both organs. Here we statement that along with profoundly modified gene manifestation profiles both in the thymus and spleen transcriptional and epigenetic rules are affected with increasing age. This is accompanied by modified manifestation of CD surface markers and the composition of T cell populations in both organs. Results Ko-143 Age-dependent gene manifestation changes do not happen simultaneously in different organs To get an understanding of age-dependent changes that happen in main and secondary immune organs we profiled mRNA transcripts from thymus and spleen cells extracted from 1-month (young) 4 (mature) or 18-month-old male Long Evans rats using Illumina? RatRef12 BeadChips (S1). The number of genes affected by manifestation changes assorted with age and cells. In thymus changes in the manifestation of 1034 genes were detected between young and old animals whereas only 86 genes were affected between 1-month and 4-month-old animals. In spleen high numbers of manifestation changes were observed when comparing aged and mature animals to young animals (2196 and 2019 genes respectively) whereas Ko-143 a low number of changes occurred between 4- and 18-month-old animals (Number ?(Figure1A).1A). The cluster analysis based on all probes displayed within the BeadChip further showed that for spleen manifestation profiles of adult and old animals clustered more closely whereas for thymus profiles of young and mature animals clustered more closely (Number ?(Figure1B1B). Number 1 Cluster analysis and practical classification of gene manifestation results. (A) Quantity of differentially indicated genes when comparing different age groups; y is definitely Ko-143 young m is definitely adult and o is definitely aged. (B) Cluster analysis based on all probes displayed on … When comparing the total gene manifestation changes that happen between young and old animals in spleen and thymus 516 genes are differentially indicated in both cells whereas 1591 are spleen-specific and 518 thymus-specific changes (Number ?(Number1C).1C). The genes that were generally differentially indicated in both spleen and thymus affected biological processes of cell cycle DNA replication immune response and epigenetics (Numbers ?(Numbers1C 1 S2). For better understanding of the practical implications of these manifestation changes practical classification was performed. In both cells aging was associated with an increase in the number of differentially indicated genes involved in cell cycle rules DNA replication and senescence. Alongside those genes involved in DNA restoration epigenetic rules apoptosis and immune response were also.