(A). of aged mice after stimulation. Importantly, while adoptive transfer of purified Tg CD8 T cells of young or aged mice into young wild type mice resulted in expansion of the Tg CD8 T cells of both ages after LCMV infection, the expansion of the Tg T cells from aged mice was significantly decreased compared with that of the Tg T cells from young mice. However, while the number of IFN- secreting Tg CD8 T cells from aged mice was significantly decreased compared to that of young mice, the percentages of Tg CD8 T cells producing IFN- was similar in Mouse monoclonal to Metadherin young and aged mice, demonstrating that proliferation, but not function, of the Tg CD8 T cells of aged mice was impaired. Importantly, chronological age alone was not sufficient to predict an altered proliferative response; rather, expression of high levels of CD44 on CD8 T cells of aged mice reflected a decreased proliferative response. These results reveal that alterations intrinsic to CD8 T cells can contribute to the age-associated defects in the primary CD8 T cell response during viral infection. experimental settings may be due to an alteration of early activation with aging (Jiang et al., 2007). A recent study (Decman et al., 2010) has demonstrated that cell-intrinsic defects with aging can also affect the memory CD8 T cell function. These investigators found that when equal numbers of flu NP366-374-specific memory CD8 T cells from either young or aged mice were transferred into congenic young mice, the specific memory CD8 T cells L-Ascorbyl 6-palmitate from aged mice did not expand as well as those from young mice after infection with vaccinia virus- NP366-374, demonstrating that intrinsic defects in memory CD8 T cells of aged mice may impair their L-Ascorbyl 6-palmitate ability to mount vigorous recall responses during secondary flu infection (Decman et al., 2010). They further demonstrated that qualitative changes in virus specific precursors can lead to a defective CD8 T cell response with aging (Decman et al., 2012). Since the frequency of specific CD8 T cells is very low in both young and aged wild type (wt) na?ve mice, it has been difficult to directly examine whether there is an intrinsic defect in the primary CD8 T cell response. Recently, investigation of specific T cell immune responses has been made easier by the generation of CD8 TCR transgenic (Tg) mice in which the majority of CD8 T cells have receptors that recognize one specific epitope. However since aged Tg mice are not commercially available, it is difficult to perform studies to directly examine intrinsic defects in na?ve Tg CD8 T cells with aging. In one study, Li et al (Li et al., 2002) found that after stimulation with specific antigen vs and with the specific CD8 T cell epitope of LCMV L-Ascorbyl 6-palmitate in the presence of APCs of young wt mice, both the activation and proliferation of the purified Tg CD8 T cells from aged P14 mice were significantly impaired compared with those of CD8 T cells from young P14 mice. Importantly, while LCMV infection led to expansion of adoptively transferred Tg CD8 T cells from young and aged P14 mice in young recipient mice, the expansion was significantly less in the T cells from aged mice compared to those from young mice. These results clearly demonstrate that cell-intrinsic alterations can contribute to the age-associated defects in primary CD8 T cell response to antigens or viral infection. 2. Materials and Methods 2.1. Mice and lymphocytic choriomeningitis virus (LCMV) Six to eight week old wt Thy1.1+ C57BL/6 (B6, H-2b) mice were purchased from The Jackson laboratory (Bar Harbor, ME). Six to eight week old P14 (LCMV GP33-41 TCR-Tg, Thy1.2+) mice (Brandle et al., 1991) were obtained from Taconic Farms (Hudson, NY), with some being aged to 21C22 months in the animal facilities at Drexel University (Philadelphia, PA). All experiments were conducted with the approval of the Institutional Animal Care and Use Committee (IACUC) at Drexel University. All mice were maintained in AAALAC-approved barrier facilities. Mice were allowed to acclimate for at least one week in the animal facilities prior to use, and mice exhibiting enlarged spleens or tumors were eliminated from this study. LCMV Armstrong was propagated and the titers were determined by plaque assay as described previously (Ahmed et al., 1984). 2.2. Cell isolation and purification Mice were sacrificed by CO2 asphyxiation followed L-Ascorbyl 6-palmitate by cervical dislocation, and spleens were aseptically removed. Lymphocytes were isolated using 0.83% ammonium chloride. Mononuclear cells were resuspended in RPMI-1640 containing 10% FBS, L-glutamine,.