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PubMed2001

In vivo-matured Langerhans cells continue to take up and process native proteins unlike in vitro-matured counterparts.

We have been able to identify the cell subset derived from Langerhans cells in the total dendritic cell population of the peripheral lymph node and hence to follow their trafficking under normal physiological conditions as well as upon skin irritation. As expected, the rapid mobilization of Langerhans cells triggered by inflammatory signals into the draining lymph node correlated with an up-regulation of costimulatory molecules and with an enhanced immunostimulatory capacity. Surprisingly, however, these cells, instead of shutting down, maintain the capacity to capture and process protein Ags during the couple of days they stay alive in stark contrast to in vitro-matured dendritic cells.

Animals↗
PubMed2002

Rat peripheral CD4+CD8+ T lymphocytes are partially immunocompetent thymus-derived cells that undergo post-thymic maturation to become functionally mature CD4+ T lymphocytes.

CD4+CD8+ double-positive (DP) T cells represent a minor subpopulation of T lymphocytes found in the periphery of adult rats. In this study, we show that peripheral DP T cells appear among the first T cells that colonize the peripheral lymphoid organs during fetal life, and represent approximately 40% of peripheral T cells during the perinatal period. Later their proportion decreases to reach the low values seen in adulthood. Most DP T cells are small size lymphocytes that do not exhibit an activated phenotype, and their proliferative rate is similar to that of the other peripheral T cell subpopulations. Only 30-40% of DP T cells expresses CD8beta chain, the remaining cells expressing CD8alphaalpha homodimers. However, both DP T cell subsets have an intrathymic origin since they appear in the recent thymic emigrant population after injection of FITC intrathymically. Functionally, although DP T cells are resistant to undergo apoptosis in response to glucocorticoids, they show poor proliferative responses upon CD3/TCR stimulation due to their inability to produce IL-2. A fraction of DP T cells are not actively synthesizing the CD8 coreceptor, and they gradually differentiate to the CD4 cell lineage in reaggregation cultures. Transfer of DP T lymphocytes into thymectomized SCID mice demonstrates that these cells undergo post-thymic maturation in the peripheral lymphoid organs and that their CD4 cell progeny is fully immunocompetent, as judged by its ability to survive and expand in peripheral lymphoid organs, to proliferate in response to CD3 ligation, and to produce IL-2 upon stimulation.

Aging↗
PubMed1975

Interrelationships of dental maturity, skeletal maturity, height and weight from age 4 to 14 years.

The correlations of dental mineralization stages, skeletal mineralization, body-height and weight were determined for each year between age 4 and 14 for 121 boys and 111 girls of the serial experimental group of the Burlington Growth Centre. Dental development related more strongly to morphological development than to skeletal development in both sexes, and skeletal age was more strongly related to morphological age than to dental stage. The relationship of individual teeth to skeletal age, height and weight were different but consistent in a sex-specific pattern. In males, both skeletal mineralization and dental mineralization, particularly of the first molars, were more closely related to height than to weight. In the females, skeletal and dental mineralization, especially of the second molars, were more closely related to weight from age 7 than to height. These relationships were significant in both pre-adolescent and adolescent years. In both these periods, skeletal age and body size related most strongly to late stages of tooth formation. Hence, from an early age, the stages of dental, skeletal and morphological maturation were significantly interrelated in a pattern that was specific for individual teeth and for sex.

Adolescent↗
PubMed1981

Maturation of bone marrow lymphocytes. IV. Kinetics of maturation and renewal of lymphocytes expressing Ia and H-2K antigens.

As part of a series of studies on bone marrow lymphocyte differentiation, I region-associated (Ia) and H-2K antigens have been quantified on small lymphocytes in mouse bone marrow and spleen, and correlated with cell renewal. Ia antigens were revealed radioautographically on some marrow small lymphocytes, the antigen density being lower than on spleen cells. Kinetic studies, combining surface rosetting and [3H]-thymidine labelling, showed that most Ia antigen-bearing lymphocytes were newly formed cells, rapidly renewed in the marrow. Ia antigens were first expressed after a post-mitotic lag period and increased in density with time. A minority of Ia antigen-bearing small lymphocytes in the marrow and a large majority of those in the spleen remained unlabelled by [3H]-thymidine, infused for 3-5 days. Some putative progenitor cells in the marrow showed surface Ia antigens of medium density. In neonatal mice the incidence and density of Ia antigens were low in the marrow and spleen, reaching adult values by 4 and 10 weeks of age, respectively. In contrast, H-2K antigens were expressed in high density on all lymphoid cells in both marrow and spleen from early postnatal life onwards. Thus, Ia antigens, but not H-2K antigens, behave as differentiation markers in the maturation of small lymphocytes produced in the bone marrow. In addition, some Ia antigen-bearing small lymphocytes in adult bone marrow are slowly renewed cells, putative long-lived immigrants from the recirculating pool.

Age Factors↗
PubMed1981

Control of B-cell maturation in mice. I. Increased B-cell maturation in vitro by bone marrow protected during whole body irradiation.

The possibility of a homeostatic control on the production of B cells was studied in CBA mice following whole body irradiation (750 rads). Bone marrow cells from femurs shielded from irradiation were taken at 24 h and the number of surface immunoglobulin positive cells assessed with a fluorescence-activated cell sorter after 24 h in vitro. The cells from the irradiated shielded mice showed greater absolute number of 'bright' B cells with a high density of surface immunoglobulin (mean increase 60%--100%) than cells from control unirradiated mice. These bright B cells did not incorporate (3H) thymidine in vitro and treatment with hydroxyurea (an inhibitor of DNA synthesis) did not prevent their increase. It was concluded that the increased number of bright B cells in vitro arose from augmented maturation or differentiation and not from a proliferative process.

Animals↗