Age-related decline in humoral immunity caused by the selective loss of TH cells and decline in cellular immunity caused by the impaired migration of inflammatory cells without a loss of TDTH cells in SAMP1 mice

The influence and impact of ageing and immunosenescence (ISC) on adaptive immunity during multiple sclerosis (MS) and the animal counterpart experimental autoimmune encephalomyelitis (EAE)

The human ageing process encompasses mechanisms that effect a decline in homeostasis with increased susceptibility to disease and the development of chronic life-threatening illness. Increasing age affects the immune system which undergoes a progressive loss of efficiency, termed immunosenescence (ISC), to impact on quantitative and functional aspects of innate and adaptive immunity. The human demyelinating disease multiple sclerosis (MS) and the corresponding animal model experimental autoimmune encephalomyelitis (EAE) are strongly governed by immunological events that primarily involve the adaptive arm of the immune response. MS and EAE are frequently characterised by a chronic pathology and a protracted disease course which thereby creates the potential for exposure to the inherent, on-going effects and consequences of ISC. Collective evidence is presented to confirm the occurrence of established and unendorsed biological markers of ISC during the development of both diseases. Moreover, results are discussed from studies during the course of MS and EAE that reveal a premature upregulation of ISC-related biomarkers which indicates untimely alterations to the adaptive immune system. The effects of ISC and a prematurely aged immune system on autoimmune-associated neurodegenerative conditions such as MS and EAE are largely unknown but current evaluation of data justifies and encourages further investigation.

Skin Immunity

Skin is the largest organ of the body with a complex network of multitude of cell types that perform plastic and dynamic cellular communication to maintain several vital processes such as inflammation, immune response including induction of tolerance and disease prevention, wound healing, and angiogenesis. Of paramount importance are immunological functions of the skin that protect from harmful exposure coming from external and internal environments. Awareness of skin immunity can provide a better comprehension of inflammation, autoimmunity, cancer, graft-versus-host disease, vaccination, and immunotherapy approaches. This paper will update on what we currently know about immune sentinels contributing to skin immunity.

5,7-Dihydroxyflavone Analogues May Regulate Lipopolysaccharide-Induced Inflammatory Responses by Suppressing IκBα-Linked Akt and ERK5 Phosphorylation in RAW 264.7 Macrophages

We studied the anti-inflammatory activity of twelve 5,7-dihydroxyflavone analogues in lipopolysaccharide- (LPS-) stimulated RAW 264.7 macrophages. We found that chrysin (1) and 4′-methoxytricetin (9) showed relatively significant anti-inflammatory activity and low cytotoxicity. Moreover, 1 and 9 recovered the expression levels of iNOS and COX2, as well as those of the intracellular inflammatory mediators IL-1β and IL-6, which were upregulated by LPS stimulation. In addition, 1 and 9 actively regulated the phosphorylation of IκBα, leading to the activation of NFκB. Phosphorylation of Akt and ERK5 (upstream of NFκB) by LPS stimulation was significantly regulated by 1 and 9, as well as by BIX 02189 and LY 294002, which are phosphorylation inhibitors of ERK5 and Akt, respectively. The results suggest that compounds 1 and 9 may suppress the levels of iNOS and COX2 by regulating phosphorylation of Akt, ERK5, and IκBα and thus NFκB-related signaling pathways, resulting in anti-inflammatory effects in the cells. Because 1 and 9 showed low cytotoxicity and regulated both PGE₂ and NO production caused by inflammatory responses, they may hold promise as natural anti-inflammatory agents.

Altered regulation of CXCR4 expression during aging contributes to increased CXCL12-dependent chemotactic migration of CD4(+) T cells

Chemokine-dependent migration of T lymphocytes assures recirculation of naïve T cells to secondary lymphoid organs and tissue-specific trafficking of memory-effector T cells. Previous studies carried out in rodents have demonstrated age-associated modulation of the expression of chemokine receptors such as CXCR4 and CCR5; however, little is known about the molecular mechanisms that regulate receptor expression and turnover in T cells, during advancing age in humans. Our recent results demonstrating increased chemotactic migration in response to CXCL12 in CD4(+) T cells obtained from the elderly, as compared to those from young donors, led us to hypothesize that increase in surface expression, because of altered endocytic regulation of CXCR4 on T cells during aging, might be directly responsible for increased migration toward CXCL12. Studies presented here demonstrate a significant increase in the surface expression of CXCR4 in CD4(+) T cells from elderly human donors, relative to those from the young. Additionally, CXCL12-mediated endocytosis of CXCR4 was differentially regulated during aging, which could be attributed to alterations in the ubiquitination of CXCR4. Thus, altered ubiquitination of CXCR4 may contribute to the increased surface expression and enhanced T-cell migration to chemotactic stimuli in the elderly.

Immune responses in the skin in old age

A marked increase in the susceptibility to cutaneous infections and malignancies has been observed in older humans indicating that cutaneous immunity becomes defective with age. In this review we will focus on recent developments in the understanding of age-related changes in immune function of the skin with a particular emphasis on how alterations in the interaction between cells involved in innate and adaptive immunity leads to decreased cutaneous antigen-specific T cell immunosurveillance.

Local immune response to respiratory syncytial virus infection is diminished in senescence-accelerated mice

The effect of ageing on the local defence system against respiratory syncytial virus (RSV) infection was investigated using an aged mouse model of the senescence-accelerated mouse (SAM) strain P1. Following intranasal infection with RSV, SAM-P1 mice showed a marked loss in weight, with elevated virus growth in the lungs and prolonged virus shedding. The increased susceptibility to RSV infection was associated mainly with diminished cellular immunity by local virus-specific cytotoxic T lymphocytes and natural killer cells. The deficiency in cellular immune responses was due to a lack of clonal expansion of CD4+ and CD8+ T lymphocytes, together with an imbalance of T-helper type 1 (Th1)/Th2 cytokine production in the respiratory tract, including the lungs. Furthermore, the production of virus-specific local IgA antibody was restrained. Prolonged virus loading in the lungs of SAM-P1 mice caused a massive infiltration of CD16+/32+ inflammatory cells, which was one factor responsible for severe pneumonia. The adoptive transfer of immune-competent spleen cells achieved an appreciable protection for SAM-P1 mice against RSV challenge infection. These results suggested that age-related immune dysfunction, especially defects in cellular immune responses, accounts for the increased morbidity and mortality in RSV infection of the elderly.

Sustained thymopoiesis and improvement in functional immunity induced by exogenous KGF administration in murine models of aging

Age-related thymopoietic insufficiency has been proposed to be related to either defects in lymphohematopoietic progenitors or the thymic microenvironment. In this study, we examined whether keratinocyte growth factor (KGF), an epithelial cell-specific growth factor, could increase thymopoietic capacity in aged mice by restoration of the function of thymic epithelial cells (TECs). The thymic cellularity in KGF-treated aged mice increased about 4-fold compared to placebo-treated mice, resulting in an equivalent thymic cellularity to young mice. Enhanced thymopoiesis was maintained for about 2 months after a single course of KGF, and sustained improvement was achieved by administration of monthly courses of KGF. With the enhanced thymopoiesis after KGF treatment, the number of naive CD4 T cells in the periphery and T-cell-dependent antibody production improved in aged mice. KGF induced increased numbers of TECs and intrathymic interleukin-7 (IL-7) production and reorganization of cortical and medullary architecture. Furthermore, KGF enhanced thymopoiesis and normalized TEC organization in klotho (kl/kl) mice, a model of premature degeneration and aging, which displays thymopoietic defects. The result suggests that TEC damage is pathophysiologically important in thymic aging, and KGF therapy may be clinically useful in improving thymopoiesis and immune function in the elderly.

Neurotrophic Effect of Magnolol in the Hippocampal CA1 Region of Senescence-Accelerated Mice (SAMP1)

Magnolol has neurotrophic effects in primary cultured rat cortical neurons, which are expressed as the promotion of neurite outgrowth and neuronal survival. In this study, we investigated the protective effect of magnolol against age-related neuronal loss in the hippocampus using senescence-accelerated mouse (SAMP1). Magnolol (5, 10 mg/kg) was orally administered once a day for 14 d to 2- or 4-month-old mice, and evaluation was carried out when the mice were 4 or 6 months old. The density of neurofibrils decreased with aging in the stratum radiatum of the CA1 region in the hippocampus of SAMP1, not SAMR1. Treatment with magnolol significantly prevented the decrease of neurofibrils in the CA1, when it was administered in 2-month-olds. However, administration at 4 months of age did not result in a preventive effect. These findings suggest that the administration of magnolol before the initiation of neuronal loss may result in a protective effect in the hippocampus.

Increased incidence of pathological and clinical prostate cancer with age: age related alterations of local immune surveillance

PURPOSE

The incidence of prostate cancer dramatically increases with age. The etiology still awaits elucidation, and the question as to why it is so prominently a disease of aging remains unanswered. We offer an explanation by suggesting an age related deficient immune surveillance.

MATERIALS AND METHODS

Reports published in the scientific literature with relevance to cancer and immunity, immune senescence, blood-prostate barrier and immune privilege were identified using MEDLINE.

RESULTS

The existence of a blood-prostate barrier is a fair assumption, and the prostate may be considered an immune privileged site. With aging the prostate, a priori immunologically under surveilled, probably becomes more and more so. There is impaired function, transmigration and probably penetration into the gland of natural killer and other immune competent cells due to the onset of immune senescence coupled with impaired diapedesis and possible age related alterations in the blood-prostate barrier.

CONCLUSIONS

Apparently, with aging the immune surveillance of the already immune privileged prostate is progressively and further affected. This condition may result in the inability of the gland to eradicate emergent malignant cells.

Immunological memory and late onset autoimmunity

This review will address a paradox that has long fascinated scientists studying the effects of aging on the immune system. Although it has been clearly documented that B and T lymphocytes lose the ability to respond to antigenic or mitogenic stimulation with age, it has nonetheless been noted that the frequency of autoreactive antibodies is higher in older individuals. Given that the majority of the age-associated defects in immune regulation target the naïve T and B lymphocyte subsets, it has been presumed that this increase in antibodies specific for self antigens was due to changes in the B cell repertoire and/or to differences in the mechanisms responsible for generating immune tolerance in primary responses. However, in this review, we will address an alternative possibility that memory immune responses, first generated when the individual was young, may play a critical role in the appearance of serum autoantibodies by reactivation later in life (recall memory). It has recently been shown, in several different systems, that memory immunity can be maintained over the lifetime of the animal. Thus, memory B cells which are self-reactive may be harbored within an organism as it ages and the potential exists that they become re-activated at a later time, resulting in a vigorous autoreactive recall response. This may occur preferentially in older individuals due to several factors, including deficiencies in immune tolerance with age, progressive age-associated loss of tissue integrity yielding neo-self antigens, and possible re-exposure to an infectious agent which induces an autoimmune memory response through molecular mimicry. Thus, we propose that some of the autoantibodies seen in elderly patients and in older animals may have been produced by memory lymphocytes originally generated against antigens encountered during one's youth, but maintained in a tolerant (non reactive) state until a subsequent triggering event occurs. Possible implications of this model will be discussed.

Differential effects of ageing on cytokine and chemokine responses during type-1 (mycobacterial) and type-2 (schistosomal) pulmonary granulomatous inflammation in mice

Cytokine and chemokine responses during anamnestic type-1 and type-2 lung granuloma formation were evaluated in mice at 6,12,18 and 24-months of age. Lesions were induced by embolizing Sepharose beads coupled to Mycobacterium bovis purified protein derivative or soluble Schistosoma mansoni egg antigens. Type-1 inflammation was reduced by 18 months, whereas type-2 granulomas not until 24 months of age. In type-1 draining lymph nodes cultures, interferon-gamma (IFNgamma) declined to a nadir by 18, and then partly recovered at 24 months. In contrast, IL-4 was not significantly impaired in type-2 cultures until 24 months. Type-1 and 2 node cultures also displayed decreased IL-13, but paradoxically enhanced IL-5 production at 24 months. Chemokine transcripts in granulomatous lungs displayed age-related alterations. In the type-1 response, CXCL9 (monokine-induced by IFNgamma) declined with age then partly recovered at 24 months parallelling lymph node IFNgamma levels. Transcripts for MIP-2/CXCL2, IP-10/CXCL10, MCP-1/CCL2, and MCP-5/CCL12 increased at 24 months. In the type-2 response MCP-1/CCL2, MCP-3/CCL7, MCP-5/CCL12 and TARC/CCL17 collapsed at 24 months paralleling local IL-4 transcript levels, yet some chemokine transcripts such as KC/CXCL1 and eotaxin/CCL11 were unaffected. These findings suggest that cytokine and chemokine responses degrade differentially with age shifting Th1/Th2 crossregulatory pressures and local expression of chemokines.

Intestinal lymphocyte number, migration and antibody secretion in young and old rats

This study demonstrates that the mucosal immune response to cholera toxin (CT) is compromised in old rats in comparison with young animals. The total number of immunoglobulin A (IgA)-secreting cells is similar or higher in the intestinal inductor and effector sites in old animals. However, the number of specifically induced anti-CT IgA antibody-secreting cells is lower in these tissues in comparison with those in young animals. The kinetics of this immune response in the different gut-associated lymphoid tissues studied suggests that the age-associated decline in the number of anti-CT IgA-secreting cells in the intestinal mucosa reflects impaired IgA immunoblast migration. Our data from lymphocyte adoptive transfer studies indicate that factors intrinsic to both the donor cells and the host recipient influence the migration of immunoblasts from the Peyer's patches to the effector site. For example, donor cells from old donors transferred to either young or old recipient rats migrate slower than young donor lymphocytes transferred into old host animals. In vitro studies clearly indicate that ageing does not impair antibody secretion by intestinal mucosal plasma cells. Therefore, the age-related decline in the intestinal mucosal immune response, e.g. diminished specific antibody titres in intestinal lavage, reflects fewer antibody-secreting cells in the mucosa.