Chieri Kurashima

Differential age-change in the numbers of CD4+CD45RA+ DC4+CD29+ T cell subsets in human peripheral blood

Peripheral blood mononuclear cells were obtained from people ranging in age from newborn to 102 years old and analyzed by dual color flow cytometer in terms of number and percentage of various subsets of T cells, B cells and natural killer cells (CD3, 4, 5, 8, 11b, 19, 20, 21, 25, 29, 45RA and 56). Numbers of T cells (CD3+ or CD5+ cells) significantly declined at the 3rd decade as compared with those of younger people, stayed at a relatively constant level between the 3rd and the 7th decade and gradually declined thereafter. In T cell subsets, both CD4 and CD8 positive positive cells decreased with age, but a decrease was more pronounced in the latter, showing an age-related increase of CD4/CD8 ratio. The most interesting finding was a contrasting age-change in two subsets of CD4+ T cells; i.e. a subset of suppressor inducer T cells (CD4+CD45RA+ naive cells) decreased with age, while a subset of helper inducer T cells (CD4+CD29+ memory cells) increased with age. CD20+ B cells also decreased with age in a manner similar to that observed in T cells. Natural killer cells (CD56) showed an increase in numbers with age. The relationship between these changes in various subsets of peripheral blood leukocytes and the age-related decline in immune functions has been discussed.

Understanding the mechanism of the age-change of thymic function to promote T cell differentiation

Immunological functions peak at around puberty and gradually decline thereafter with advancing age. The immunological decline mainly occurs in the T cell-dependent immune system and is generally associated with an increase in not only susceptibility to infections but also incidence of autoimmune phenomena. The age-related changes in T-cell dependent immune functions can be mainly ascribed to the physiological thymic involution which starts in the early phase of life. The age-related thymic involution can be ascribed to either extrinsic or intrinsic factors. Bone marrow stem cells can be one of the extrinsic factors for the thymic involution, but their role is estimated to be marginal as compared with alteration of the thymic microenvironment. With advancing age, the thymic capacity to promote T-cell differentiation declines together with a change in the composition of T-cell subsets produced. Such an alteration of the thymic environment is responsible for the age-related change in peripheral T cells in number and in composition. Age change is observed in several intrinsic factors in the thymic environment which influence proliferation of thymocytes. These thymic intrinsic factors can either promote or inhibit proliferation of thymocytes, and promoting factors generally decrease with age with a concomitant increase in inhibitory factors. Various endocrine hormones are important extrinsic factors influencing the thymic function. In fact, physiological thymic involution can be intervened by manipulation of the endocrine system, sometimes resulting in rejuvenation of immune functions to a certain extent.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging and Immunity

The function of the immune system peaks at around puberty and gradually declines thereafter with advance in age. The age‐related decline of immunological function primarily occurs in the T cell‐dependent immune system and is generally associated with increase in susceptibility to infections as well as in incidence of autoimmune phenomena in the elderly. The age‐related change in T cell‐dependent immune functions can be ascribed to the physiological thymic atrophy which starts in an early stage of life. Emigration of T cells from the thymus to the periphery mainly takes place in the late fetal and newborn stage, and dramatically declines after puberty. In other words, the thymic capacity to promote T cell differentiation starts to change in the early stage of life in terms of quantity and quality of T cells. Thus, the composition of T cell‐subsets in the periphery gradually changes with age, resulting in the alteration of T cell functions in the elderly. The restoration of immunological functions of the aged individuals is possible and might be beneficial for them to cope with various diseases associated with aging. Physiological thymic atrophy is controlled by both extrathymic and intrathymic factors, and is not a totally irreversible process. The process of thymic atrophy might be explained by further understanding of the relationship between the neuroendocrine and the immune systems. Acta Pathol Jpn 42: 537–548, 1992.

Age influence on the thymic capacity to promote differentiation of T cells: Induction of different composition of T cell subsets by aging thymus

Three kinds of experiments were performed to see the differential effect of aging thymus on T cell differentiation in nude mice and thymectomized mice. In the experiment of thymus grafting into nude mice, the thymic capacity to promote T cell differentiation was the highest at newborn stage, and declined to 80% of the peak level at as early as 1 week of age. The level at 4 weeks of age was 50-60% of the peak level and did not greatly change thereafter with advancing age of thymus donors, up to 24 months of age. However, composition of T cell subsets differed with age of thymus graft; i.e. L3T4(CD4)+ T cells were more easily induced than Lyt-2(CD8)+ T cells by aging thymus, resulting in an increase of the ratio of L3T4+/Lyt-2+ T cells with advancing age of thymus donors. The decreased number of T cells and their subsets in the mice thymectomized at 4 weeks of age could be almost totally recovered by the grafting of newborn thymus, but less efficiently by the grafting of 24-month-old thymus. In the latter case again, L3T4+ T cells were more easily induced than Lyt-2+ T cells, resulting in an increase of the ratio of L3T4+/Lyt-2+ T cells by the grafting of the old thymus. In neonatal mice thymectomized 3 days after the birth, Lyt-2+ T cells were more severely affected than L3T4+ cells, resulting in high ratio of L3T4+/Lyt-2+ T cells. It was suggested that the capacity of the thymus to induce T cells started to decline as early as 1 week of age and did not greatly change between 4 weeks and 24 months of age. However, the composition of T cell subsets induced by the thymus changed with age, with preference for L3T4+ T cells over Lyt-2+ T cells.

Age-related change in the potential of bone marrow cells to repopulate the thymus and splenic T cells in mice

Bone marrow chimeras were produced between various combinations of young and old mice using either C57BL/6 mice only or a combination of C57BL/6 and B10.Thy-1.1 mice. The wet weight of the thymus and the number of thymocytes and splenic T cells of donor origin were assessed at appropriate intervals after the bone marrow transplantation. It was revealed that the old bone marrow was inferior to young in terms of the capacity to repopulate the thymus and splenic T cells. Moreover, some age-related qualitative changes appeared to occur in the thymocyte progenitors, as the composition of Lyt phenotype of donor-type T cells in the spleen was different between chimeras produced with young bone marrow and those with old.

Effects of a protein-free diet or food restriction on the immune system of Wistar and Buffalo rats at different ages

The effects of a protein-free diet or food restriction on the immune system were examined in two rat strains, Wistar and Buffalo, in different age-groups. Unlike Wistar rats, Buffalo rats have an unusually hyperplastic thymus and a large number of peripheral T cells. The protein-free diet (PFD) in rats resulted in marked thymic involution together with a reduction of splenic T cells, both in number and in antibody response to sheep red blood cells. The depressive effect of the PFD on the immune system was more serious in young immature rats than in older rats, but less serious in Buffalo rats having enhanced T cell functions regardless of age. Thymic involution was also accelerated in both strains of rats by feeding them a restricted amount of the control diet containing well-balanced nutrients (food restriction, FR). In the FR experiment, no significant change was observed in immune functions of Wistar rats. A slight reduction was observed in the immune functions of Buffalo rats with FR, but absolute levels were distinctly higher in Buffalo rats than in Wistar rats even after FR. These results suggested (1) that the thymic function is sensitive to protein deficiency; (2) that a well-balanced dietary condition is necessary for immunological maturation in the early stage of life and preservation of immune functions at older age; (3) that animals having higher immune functions are more resistant to malnutrition than ordinary ones.

Immunohistological study of senile brains by using a monoclonal antibody recognizing β amyloid precursor protein: significance of granular deposits in relation with senile plaques

SummaryImmunochemical analyses revealed that a monclonal antibody Am-3 recognized β amyloid precursor protein (βAPP) in senile plaques extracted from Alzheimers brain, but did not recognize β amyloid protein. Immunohistochemically, however, the staining pattern of Am-3 in frozen section of Alzheimers brain was almost the same with that of rabbit polyclonal antibody to β amyloid peptide which could recognize both β amyloid protein and βAPP. In other words, βAPP was present in senile plaques of various types, cerebrovascular amyloid and granular deposits. The granular deposits were 5–10 μm in size and laminarily distributed in the 1st, 3rd and 4th layers of cerebral cortex. They were especially abundant in 1st and 4th layers where senile plaques were usually fewer in number. Although the distribution in the cerebral cortex was different between the senile plaques and the granular deposits, the number of the granular deposits was well correlated with that of senile plaques. The granular deposits were negative in Congo-red birefringence, but contained β amyloid protein as well as βAPP fragment judging from positive staining by both Am-3 and polyclonal antibody to synthetic β amyloid peptide. Thus, they could be regarded as “pre-amyloid”.

Age-Related Changes of Cytokine Production by Murine Helper T Cell Subpopulations

Mouse CD4+ T cells were subdivided into two subsets by cell surface markers: CD44loCD45RBhi (naive) and CD44hiCD45RBlo (memory) T cells. We have reported that CD44loCD45RBhi T cells, which are predominant in young mice, decreased with age, while CD44hiCD45RBlo T cells increased. Among T cells of the same phenotype, however, it remains to be solved whether or not there is a functional difference between young and old. Therefore, we compared old with young T cells by a cytokine production assay (IL-2, IFN-gamma, IL-4 and IL-10). We employed the negative selection method by cell affinity column instead of flow cytometry as it was important to use T cells not reacted with antibodies in the cytokine production assay and as the method is quick enough to preserve the viability of the cells. Then the divided T cells were stimulated with immobilized anti-CD3 epsilon monoclonal antibody (mAb). Young CD4+ T cells produced more IL-2 and IL-4 than aged CD4+ T cells, while aged CD4+ T cells produced more IL-10 than young cells. There was no distinct age-related change in IFN-gamma production. As concerns purified CD4+ T cell subpopulations, young CD44loCD45RBhi T cells produced more IL-2 (5.3-fold higher) than young CD44hiCD45RBlo T cells and much more IL-2 (> 10-fold higher) than both groups of aged T cells. Dramatic IFN-gamma production was found in young and old CD44hiCD45RBlo T cells and young CD44loCD45RBhi T cells; however, IFN-gamma production of old CD44loCD45RBhi T cells was much lower (1/16-1/20) than that of other cell groups. IL-4 production was mainly observed in the CD44hiCD45RBlo T cell group in both young and old mice, although the former produced more IL-4 (5.2-fold higher) than the latter. There was no remarkable difference between young and old mice in the pattern of IL-10 production. These phenomena could reveal functional heterogeneity of aged CD4+ T cell subpopulations under natural conditions. Even if the surface marker is the same, the pattern of cytokine production is different between young and old cells.

Monoclonal antibody to β peptide, recognizing amyloid deposits, neuronal cells and lipofuscin pigments in systemic organs

SummaryA monoclonal antibody (AmT-1) produced against synthetic amyloid β peptide (1–28 residues) was revealed to be reactive with amyloid β peptide blotted on nitrocellulose membrane, but not with that dissolved in sodium dodecyl sulfate and electrophoresed. AmT-1 immunostained senile plaques of typical, primitive and diffuse type, as well as amyloid deposits in cerebral vessels. It also reacted with neuronal and glial cells of normal and Alzheimers disease (AD) brains. In addition, AmT-1 was also reactive strongly with lipofuscin pigments of adrenal reticular cells, and weakly with those of eccrine glands and liver cells. A rat neural cell line (PC12h) was reactive with AmT-1. By immunoelectron microscopy, a positive reaction was seen in ribosomes along the rough endoplasmic reticulum of nerve cells and PC12h cells. By immunoprecipitation, AmT1 reacted with a band at 36 kDa in the brain homogenates from Ad patients as well as from normal aged subjects. By immunoblotting analysis, AmT1 reacted with a band at 36 kDa in the cytosolic fraction of PC12 cells, and three bands (12–17 kDa) in the lipopigment fraction of the adrenal gland. These findings suggest that the cerebral amyloid deposits contain substance(s) having an epitope common to neuronal cells and lipofuscin pigments. The possible relationship between cerebral amyloid deposits and lipofuscin pigments in systemic organs is discussed.

Establishment of a monoclonal antibody against senile plaques and its application for immunohistological and immunoelectron microscopical studies in the brain of the elderly

SummaryA monoclonal antibody (Am-3) was produced against senile plaques in the brain of a patient with Alzheimers disease. Am-3 was reactive with senile plaques of typical, primitive and diffuse type not only in the brain used as immunogen, but also those in the brain of 15 out of 25 autopsy cases of the aged people. Moreover, Am-3 was also reactive with granular materials of various sizes scattered in the 1st, 3rd and 4th layers of the cerebral cortices of the cases with severe dementia. Am-3 was also reactive with vessel wall of the congophilic angiopathy. By immunoelectron microscopic examination, Am-3 was positive with amyloid fibril in the core and crown of senile plaques, and in the congophilic angiopathy.