Distribution of IgM- and IgG-containing cells during the primary immune response in the rat spleen

Summary The morphology and localisation of IgM- and IgG-containing cells in the spleen of rats immunized with sheep red-blood cells (SRBC) were studied by combining immunohistochemical reactions with routine histological and histochemical methods. It was shown that IgM cells occur only in the outer periarteriolar lymphocyte sheath (PALS), whereas IgG cells are present throughout the whole PALS. It has been concluded that these cell types have different routes of migration. Both IgM- and IgG-containing cells were found in the germinal center in close relation with the extracellular immune complexes. The significance of this localisation is discussed.     

An ultrastructural and autoradiographic study of the immune response in Hyalophora cecropia pupae

Summary Membrane-bounded spherical vesicles found in rat Sertoli cells have been examined quantitatively during the cycle of the seminiferous epithelium. Most of the vesicles were localized to the basal and columnar portions of the Sertoli cell cytoplasm. The thin lateral projections of the Sertoli cells contained very few vesicles. Morphometric analysis of the basal portion of the Sertoli cell cytoplasm revealed that the volume density (V _v ) of the vesicles changed markedly during the cycle. The V _v was at its minimum (0.036) at stage VII and maximum (0.117) at stages XI-I. The vesicles were also smaller at stage VII compared to the vesicles at stages IX-V. The stage-dependent difference in the size of the vesicles was found both in the basal and the columnar portions of the Sertoli cells. At stage VII some of the vesicles appeared to be elongated much like the tubular elements of the smooth endoplasmic reticulum (SER) from which they are probably derived. The stage-dependent differences in volume density and size of the Sertoli cell vesicles may be related to cyclic biochemical variations in the Sertoli cells, and are further indications of a variation in Sertoli cell function during the cycle of the seminiferous epithelium. Whether or not this is due to an internal cycle of the Sertoli cell or to influences from adjacent germ cells remains to be determined.     

Trypanosoma lewisi: electron microscopy of the infected spleen

The spleens of Lewis rats, both normal and infected with Trypanosoma lewisi were examined by electron microscopy. Special attention was directed to clusters of splenic cells which occur in the course of the infection. The reticular cells first showed alterations of their structure by the second day of infection, with considerable surface membrane activity. By the fourth day and thereafter various cells were found gathered around the reticular cells. These cell clusters mainly contained lymphocytes, plasma cells, and erythropoietic elements in many stages of differentiation. It was not unusual that several cell types were found adjacent to the same central reticular cell. These arrays, similar in geometry to the erythropoietic island of the bone marrow, became more predominantly “plasma cell” islands as the infection progressed. Parasites were recognizable within the reticular cells, and were noted to be in regions where the cellular membranes of adjacent cells demonstrated vesiculations resembling rhopheocytosis. A further observation was the pinching off of neighboring plasma cell cytoplasm into the reticular cells.     

Fine structure of small lymphocytes in the thymus of the mouse: Qualitative and quantitative analysis by electron microscopy

Summary Thymic small lymphocytes of dd-mice were qualitatively and quantitatively studied by electron microscopy. Differences in fine structure were revealed between cortical and medullary small lymphocytes. Cortical small lymphocytes are rounded in cell outline with a round nucleus. The cytoplasm surrounding the nucleus as a narrow rim is scanty and appears relatively dense due to an abundance of free ribosomes. The cell organelles are not well developed. On the other hand, medullary small lymphocytes are more irregular in shape with uneven cell membranes. Their nuclei are also more irregular in outline with frequent infoldings of the nuclear membrane. The cytoplasm is more abundant and paler with less numerous ribosomes. The cell organelles are better developed.Quantitative analysis was made of both cortical and medullary small lymphocytes by means of the point counting method. The nuclei of both cortical and medullary small lymphocytes are almost the same in size (a diameter of 4.9 ). The cell sizes are different between cortical and medullary lymphocytes: cortical small lymphocytes with a diameter of 5.5 were smaller than medullary ones with a diameter of 6.4 .Cortical small lymphocytes are very sensitive to the destructive effects of hydrocortisone, whereas the medullary ones are resistant.Periarteriolar lymphoid sheath in the splenic white pulp, which is known to be a thymus-dependent area, contains small lymphocytes that were similar in cytological details to medullary small lymphocytes of the thymus.In the light of the recent knowledge about a recirculating long-lived small lymphocyte pool, it appears probable that medullary small lymphocytes represent a contribution to the pool and that small lymphocytes with a long life span can be cytologically identified by electron microscopy.     

Indigofera oblongifolia leaf extract regulates spleen macrophage response during Plasmodium chabaudi infection

Malaria is a major health problem that still affects numerous countries. The current study aimed to identify the role of Indigofera oblongifolia leaf extract in regulating mouse spleen macrophages during the progression of Plasmodium chabaudi infection. Three doses of the leaf extract (100, 200, and 300 mg/kg) were administered to mice inoculated with P. chabaudi infected erythrocytes. The weight of the infected mice improved after the treatment with I. oblongifolia. The infection causes disorganization of macrophage distribution in the spleen. After the mice had been treated with the leaf extract, the macrophages appeared to be reorganized in the white and red pulp areas. In addition, the I. oblongifolia leaf extract (IOLE) significantly increased the total antioxidant capacity of the mice spleens infected with P. chabaudi. The phagocytic activity of spleen macrophages was increased in the infected group as indicated by the significant decrease in the number of fluorescent particles in the spleen sections. This number increased in the mice spleens after treatment with IOLE. Based on these results, it is suggested that IOLE regulate macrophage response of the spleen during the blood stage of malaria in mice.     

Effect of the spleen extracts on primary immune response in mice]

Experiments were conducted on mice. Direct Jerne's test demonstrated a possibility of intensification of the primary immune response in the sexually mature mice under the effect of the splenic extracts. The significance of the extract dose and of the time of administration for the manifestation of the stimulating action was studied.     

Electron microscopic studies of the innervation of the human spleen

Summary The innervation of four normal human spleens was investigated by electron microscopy. Unmyelinated nerve fibers accompanied the arterial vascular system up to the arterioles of the red pulp. Neither myelinated nerve fibers nor ganglion cells were seen in the splenic hilum or in the splenic tissue itself. The nerve fibers terminated against the smooth muscle cells of the blood vessels in a manner that is typical of the autonomic nervous system. The terminal axons contained small and large granular vesicles and thus were adrenergic nerve fibers. In contrast to the results of previous studies using silver impregnation methods innervation of the red or white pulp could not be demonstrated. The findings on human spleens agree with those on mammalian spleens obtained by other authors using ultrastructural and fluorescence histochemical methods.We are indebted to Prof. Dr. K. Unsicker for his help in discussing the results     

Dendritic cells subsets mediated immune response during Plasmodium berghei ANKA and Plasmodium yoelii infection

The roles of dendritic cells (DCs) in mediating immunity against Plasmodium infection have been extensively investigated, but immune response during pathogenesis of malaria is still poorly understood. In the present study, we compared the splenic DCs phenotype and function during P. berghei ANKA (PbA) or P. yoelii (P. yoelii) infection in Swiss mice. We observed that PbA-infected mice developed more myeloid and mature DCs capable of secreting IL-12, while P. yoelii-infected mice had more plasmacytoid and immature DCs secreting higher levels of IL-10. Expression of FoxP3, IL-17, TGF-β and IL-6 were also different between these two infections. Thus, these results suggest that the phenotypic and functional subsets of splenic DCs are key factors for regulating immune responses to PbA and P. yoelii infections.     

Progesterone is involved in the maturation of murine spleen CD11c-positive dendritic cells

Progesterone (Prog), a female sex steroid hormone, not only plays an important role in the female mammary pregnancy but also influences the immune response. In the present study, murine spleen CD11c-positive dendritic cells (SDCs) were treated with various concentrations of Prog for 24 h, and their viability, phenotype, nuclear factor kappa B P65 (NF-kappaB P65), endocytosis, stimulatory capacity, and cytokine expression were analyzed. The results showed that Prog increased the expressions of MHC-II and CD40, stimulatory capacity and intracellular levels of IL-6 and IL-10, while decreased the expressions of CD54 and IL-12, endocytosis and nuclear level of NF-kappaB P65 of SDCs. These data suggested that Prog may promote the maturation of SDCs and enhance their ability to interact with T cells so as to change the course of autoimmune diseases.     

Ultrastructural changes in Paneth cells during hibernation in the ground squirrel Spermophilm lateralis

Summary The ultrastructure of Paneth cells from jejuno-ileal segments of the small intestine of the ground squirrel, S. lateralis, was examined under normal euthermic conditions and during the profoundly depressed metabolic conditions of natural hibernation. Paneth cells obtained from hibernating animals gave evidence of markedly reduced activity when compared to Paneth cells from euthermic animals. In hibernating animals, the nuclei were smaller, with less prominent nucleoli and with an increased proportion of heterochromatin. In hibernating animals, the rough endoplasmic reticulum was fragmentary and poorly organized, in contrast to the typical arrangement of concentric lamellae seen in euthermic animals. Although the total number of ribosomes was decreased in hibernating animals, there were proportionally more free ribosomes than in euthermic animals. Paneth cells from hibernating animals also contained a greater number of apical secretory granules which were smaller and more variable in electron density than granules from control animals. These ultrastructural features indicate that during hibernation the Paneth cell is relatively quiescent.Supported by U.S.P.H.S. grants RR 05411 and RR 05583 from the N.I.H.     

An analysis of the association between various synaptic parameters during cortical development

Summary Stellate cells in the rabbit adenohypophysis were observed electron microscopically under normal and experimental conditions such as lactation, thyroidectomy, adrenalectomy, or castration.In control animals stellate cells had a scanty cytoplasm surrounding the nucleus and possessed slender processes extending between granulated cells. The processes were interconnected by desmosomes to form a meshwork. In the cytoplasm, abundant microfilaments were present as well as ill-developed ordinary cell organelles, but secretory granules were absent.In the adenohypophysis of experimental groups, in which the granulated cells underwent characteristic changes, stellate cells also showed remarkable morphological alterations which were similar in all groups. In general, they became hypertrophied, and contained a well-developed Golgi apparatus and rough-surfaced endoplasmic reticulum. Lysosomes or lipid droplets were frequently encountered. Between adjacent stellate cells, intercellular canals were markedly developed and many microvilli were noticed.Based on the above data, it is suggested that the stellate cells are not only sustentacular elements, but play an important role in the function of the adenohypophysis, such as the supply of materials to granulated cells or the disposal of waste products.This investigation was supported in part by the Ministry of Education, Science and Culture, Japan     

Ontogeny of the immune system inSebastiscus marmoratus: Histogenesis of the lymphoid organs and effects of thymectomy

Synopsis The ontogenetic development of the immune system in a marine teleostSebastiscus marmoratus was studied by histological examination and removal of the thymus. The pronephros and the spleen had been differentiated at the time of birth and contained small numbers of haemopoietic cells. In contrast to most vertebrates, the rudiments of the thymus were first visible 1 week post-birth in the dorsoposterior part of the pharynx, the same location as in the adults. However, small lymphocytes first appeared in the thymus of fish at 3 weeks of age, followed by the pronephros at 4 weeks and the spleen at 6 weeks. Complete or partial suppression of the antibody response to sheep red blood cells (SRBC) occurred in fish that were thymectomized at 1.5 months of age and immunized 2 weeks later, and a marked decrease in lymphocytes was observed in the pronephros and spleen. The thymectomy of adult fish also caused reduced serum antibody titres in fish immunized 1 month after the operation. These results suggest that the thymus plays an essential role in the development of the immune system and its functions continue into adult life.     

Cellular immune response to an engineered cell-based tumor vaccine at the vaccination site

The engineered expression of the immune co-stimulatory molecules CD80 and CD137L on the surface of a neuroblastoma cell line converts this tumor into a cell-based cancer vaccine. The mechanism by which this vaccine activates the immune system was investigated by capturing and analyzing immune cells responding to the vaccine cell line embedded in a collagen matrix and injected subcutaneously. The vaccine induced a significant increase in the number of activated CD62L(-) CCR7(-) CD49b(+) CD8 effector memory T cells captured in the matrix. Importantly, vaccine responsive cells could be detected in the vaccine matrix within a matter of days as demonstrated by IFN-gamma production. The substitution of unmodified tumor cells for the vaccine during serial vaccination resulted in a significant decrease in activated T cells present in the matrix, indicating that immune responses at the vaccine site are a dynamic process that must be propagated by continued co-stimulation.     

Thyroidectomy cells and their response to thyrotrophin releasing hormone (TRH) in the rat

Summary Thyroidectomy cells of the rat pituitary gland were studied by the peroxidase-antibody labeling procedure and by electron microscopy. Secretory granules accumulated in these cells in response to a short-term treatment with thyroxine, and the cells were then reactive to the peroxidase-antibody labeling procedure. An intravenous injection of synthetic thyrotrophin releasing hormone (TRH) to thyroxine-treated, thyroidectomized rats provoked an acute and active extrusion of secretory granules from the thyroidectomy cells. The secretory granules in these cells were mostly haloed after primary fixation in osmium tetroxide. It is concluded that TRH causes thyroidectomy cells to release their secretory granules, and presumably TSH, by the usual process of exocytosis or granule extrusion.This study was supported by USPHS Grant AM 12583.