Djikić Jasmina, Nacka-Aleksić Mirjana, Pilipović Ivan, Kosec Duško, Arsenović-Ranin Nevena, Stojić-Vukanić Zorica, Dimitrijević Mirjana, Leposavić Gordana
Department of Physiology, Faculty of Pharmacy, University of Belgrade, 450 Vojvode Stepe, 11221 Belgrade, Serbia.
Immunology Research Centre "Branislav Janković", Institute of Virology, Vaccines and Sera "Torlak", 458 Vojvode Stepe, 11221 Belgrade, Serbia.
J Neuroimmunol. 2015 Jan 15;278:123-35. doi: 10.1016/j.jneuroim.2014.12.014. Epub 2014 Dec 18.
The study was undertaken considering age-related changes in susceptibility to experimental autoimmune encephalomyelitis (EAE) and a putative role of spleen in pathogenesis of this disease. The phenotypic and functional characteristics of T splenocytes were examined in young (3-month-old), middle-aged (8-month-old) and aged (26-month-old) Dark Agouti rats immunized for EAE with rat spinal cord in complete Freund's adjuvant. The rat susceptibility to EAE induction, as well as the number of activated CD4+CD134+ lymphocytes retrieved from their spinal cords progressively decreased with aging. To the contrary, in rats immunized for EAE the number of activated CD4+ splenocytes, i.e., CD4+CD134+, CD4+CD25+FoxP3- and CD4+CD40L+ cells, progressively increased with aging. This was associated with age-related increase in (i) CD4+ splenocyte surface expression of CD44, the molecule suggested to be involved in limiting emigration of encephalitogenic CD4+ cells from spleen into blood and (ii) frequency of regulatory T cells, including CD4+CD25+FoxP3+ cells, which are also shown to control encephalitogenic cell migration from spleen into the central nervous system. In favor of expansion of T-regulatory cell pool in aged rats was the greater concentration of IL-10 in unstimulated, Concanavalin A (ConA)- and myelin basic protein (MBP)-stimulated splenocyte cultures from aged rats compared with the corresponding cultures from young ones. Consistent with the age-related increase in the expression of CD44, which is shown to favor Th1 effector cell survival by interfering with CD95-mediated signaling, the frequency of apoptotic cells among CD4+ splenocytes, despite the greater frequency of CD95+ cells, was diminished in splenocyte cultures from aged compared with young rats. In addition, in control, as well as in ConA- and MBP-stimulated splenocyte cultures from aged rats, despite of impaired CD4+ cell proliferation, IFN-γ concentrations were greater than in corresponding cultures from young rats. This most likely reflected increased abundance of IFN-γ-producing cells in splenocyte cultures from aged compared with young rats. The diminished CD4+ cell proliferation in response to ConA and MBP in splenocyte cultures from aged compared with young rats could be, at least partly, associated with an enhanced splenic expression of iNOS mRNA in aged rats. Thus, the study suggests that age-associated changes leading to entrapping of activated CD4+ cells in the spleen could contribute to the restriction in development of EAE in aged rats.
本研究旨在探讨与年龄相关的实验性自身免疫性脑脊髓炎（EAE）易感性变化以及脾脏在该疾病发病机制中的潜在作用。在以完全弗氏佐剂中的大鼠脊髓免疫诱导EAE的年轻（3个月大）、中年（8个月大）和老年（26个月大）的Dark Agouti大鼠中，检测了脾T细胞的表型和功能特征。随着年龄增长，大鼠对EAE诱导的易感性以及从其脊髓中回收的活化CD4⁺CD134⁺淋巴细胞数量逐渐减少。相反，在免疫诱导EAE的大鼠中，活化的CD4⁺脾细胞数量，即CD4⁺CD134⁺、CD4⁺CD25⁺FoxP3⁻和CD4⁺CD40L⁺细胞数量，随着年龄增长而逐渐增加。这与以下年龄相关的增加有关：（i）CD4⁺脾细胞表面CD44的表达，该分子被认为参与限制致脑炎性CD4⁺细胞从脾脏向血液中的迁移；（ii）调节性T细胞的频率，包括CD4⁺CD25⁺FoxP3⁺细胞，这些细胞也被证明可控制致脑炎性细胞从脾脏向中枢神经系统的迁移。与老年大鼠中T调节细胞池的扩大相一致的是，与年轻大鼠相应培养物相比，老年大鼠未刺激的、刀豆蛋白A（ConA）和髓鞘碱性蛋白（MBP）刺激的脾细胞培养物中IL-10的浓度更高。与年龄相关的CD44表达增加一致，CD44通过干扰CD95介导的信号传导促进Th1效应细胞存活，与年轻大鼠相比，老年大鼠脾细胞培养物中CD4⁺脾细胞中凋亡细胞的频率尽管CD95⁺细胞频率更高，但仍有所降低。此外，在对照以及老年大鼠的ConA和MBP刺激的脾细胞培养物中，尽管CD4⁺细胞增殖受损，但IFN-γ浓度高于年轻大鼠的相应培养物。这很可能反映了与年轻大鼠相比，老年大鼠脾细胞培养物中产生IFN-γ的细胞数量增加。与年轻大鼠相比，老年大鼠脾细胞培养物中对ConA和MBP反应的CD4⁺细胞增殖减少至少部分可能与老年大鼠脾脏中iNOS mRNA表达增强有关。因此，该研究表明，导致活化的CD4⁺细胞滞留在脾脏中的年龄相关变化可能有助于限制老年大鼠中EAE的发展。
