Thymic nurse cells are multicellular complexes located in the subcortical area of the thymus of all avian, mammalian and amphibian species investigated so far. Since their first description in 1980 many studies have been carried out to characterize their morphological and functional properties. The purpose of this review is to summarize recent morphological as well a functional analyses of chicken thymic nurse cells which suggest a role of these cell complexes in T cell selection.

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Placental hormones: I. Immunofluorescence studies of the localization of chorionic gonadotrophin, placental lactogen and prolactin in human and rat placenta and in the endometrium of pregnant rats.

Chorionic gonadotrophin (CG), placental lactogen (PL) and prolactin (PRL) were localized in sections of human and rat placenta using the indirect immunofluorescence technique. Antisera were absorbed with homologous and unrelated antigens by affinity chromatography or complexed with their respective antigens. To exclude binding of IgG and immune complexes to Fc-receptor in chorionic tissue, thus leading to erroneous results, sections were preincubated with an excess of rat IgG. The results indicate that, in the human placenta, human CG (hCG) and human PL (hPL) can be identified in the syncytiotrophoblast. Using antibodies to hPRL fluorescence was found in giant cells within the cytotrophoblastic islands in the intervillous space and in cytotrophoblastic cells within placental septa. In the rat placenta rat PL (rPL) and rat PRL (rPRL) could be identified in the giant cells of the basal zone. Furthermore rPRL/rPL was localized in the endometrium and adjacent decidial cells of rat pregnancy. No staining of chorionic cells was detected using antibodies against hCG and bLH, which cross-reacted with rLH. These experiments provide further evidence that the rat placenta is unlikely to produce a CG/LH-like hormone.

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Placental hormones: II. Immunofluorescence studies of the localization of prolactin/placental lactogen- and human chorionic gonadotrophin-receptors in human and rat placenta.

Human term placentae and rat placentae of gestation day 15 and 17 were examined for the localization of prolactin (PRL)/placental lactogen (PL) and human chorionic gonadotrophin (hCG) receptors by means of an immunofluorescence technique in order to determine possible target cells for PRL/PL and hCG and to obtain indirect evidence for the localization of steroid producing cells. In the human placenta, PRL/PL- and hCG-receptors were observed in the syncytiotrophoblast of the chorionic villi and in the giant cells of placental septa and cytotrophoblastic islands in the intervillous space. In the rat placenta, PRL/PL- and hCG-binding was localized mainly to the giant cells and vacuolated glycogen cells of the basal zone.

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Immunity and aging.

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The aging immune system: primary and secondary alterations of immune reactivity in the elderly.

The function of the immune system is known to decline in the elderly. The present communication will show that, similar to the situation in children, it is necessary to distinguish between primary and secondary alterations of the immune reactivity in the elderly. The primary immunological change in the elderly is the age-dependent intrinsic decline of immune responsiveness that is also observed in healthy persons, i.e., those selected according to the criteria of the SENIEUR Protocol of EURAGE (European Community Concerted Action on Aging). Secondary immunological changes are due to underlying diseases and various environmental factors, including diet, drug intake, physical activity, etc. While primary immunodeficiencies of the elderly are not, or only to a very minor extent, presently influenced by therapeutic measures, secondary alterations of the immune function offer further possibilities for corrective measures. Clinically, the consequences of impaired immune function in the elderly include increased susceptibility to infectious disease, the emergence of tumors, and increased autoimmune reactions, the latter albeit often without concomitant autoimmune disease. In fact, autoimmune diseases in generally begin to develop at younger ages, but their consequences are major factors affecting the quality of life of the elderly. Investigations of basic molecular and cellular aspects of the aging immune system are, therefore, of theoretical, clinical and socioeconomic interest.

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Role of heat shock protein 65/60 in the pathogenesis of atherosclerosis.

Investigations in rabbits and humans have provided experimental evidence that autoimmune reactions play a major role in the initial stages of the development of atherosclerosis. These involve the infiltration of the arterial intima with T cells reacting with heat shock protein (hsp) 65/60 and the occurrence of anti-hsp 65/60 antibodies. This early immunologically mediated stage of atherosclerosis is still reversible but if additional risk factors, such as high cholesterol levels, come into effect, severe mostly irreversible lesions develop.

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Altered immunoendocrine dialogue in autoimmune disease.

Autoimmune diseases have a multifactorial pathogenesis including essential genetic and nonessential modulatory factors. Among the essential factors, not only should genes coding for an abnormal reactivity of the immune system be considered, but we have, in addition, provided experimental evidence for the existence of genes responsible for a susceptibility of the target organ/structure for the autoimmune attack. Only when both sets of essential genes are present does an autoimmune disease develop at all. The modulatory factors then determine the final outcome in each case. The present contribution discusses the immunomodulating role of glucocorticoid and sex steroids focussing on the Obese Strain (OS) of chickens, a model for Hashimoto thyroiditis.

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