Estudio histológico y nueva interpretación de las estructuras queratinizadas en las amigdalas palatinas humanas / Histological study and new interpretation of the keratinized structures in the human palatin tonsils

Actualmente se reconoce a la epidermis como un órgano adscrito al sistema inmunológico, habiéndose comprobado que sus células epiteliales suministran el sustrato para la maduración post-tímica de los linfocitos T. Ya que existen muchas analogías entre los queratinocitos epidérmicos y las células reticuloepiteliales del timo, similitudes no sólo morfológicas sino bioquímicas e inmunológicas en donde la queratina parece jugar un rol trascendente, hemos examinado las zonas queratinizadas en amígdalas palatinas obtenidas por extirpación quirúrgica, con el fin de determinar la relación entre los fenómenos inflamatorios y la presencia de formaciones que se asemejan a los corpúsculos tímicos de Hassall. Dichas formaciones, que dan las reacciones histológicas e histoquímicas propias de la queratina, se ubican tanto en regiones alejadas como cercanas al lumen de las criptas amigdalares, y con mayor frecuencia en áreas desprovistas de inflamación, a juzgar por la escasez de polimorfonucleares y demás células asociadas al proceso las que, sin embargo, son frecuentes en otras regiones del epitelio. Nuestras comprobaciones nos permiten concluir que estas estructuras no representan zonas de queratinización superficial en respuesta a estímulos irritativos, y que su presencia en este lugar podría obedecer a una razón funcional semejante a la que condiciona la formación de los corpúsculos tímicos

Fine structure of the thymus in the adult cling fish Sicyases sanguineus (Pisces, Gobiesocidae).

The structure of the thumus in adult specimens of a marine teleost, the cling fish Sicyases sanguineus, has been studied by light and transmission electron microscopy. Most cling fishes have an outer thymus located beneath the opercular epithelium. A few of them, however, have a large inner thymus besides a poorly developed outer thymus. In the well-developed outer thymus of cling fish there are three different zones: outer cortex, inner cortex, and medulla. The inner cortex is similar to the cortical region of the thumus in other vertebrates, whereas the outer cortex is a specialized lympho-epithelial zone containing cystic cells (also present in medullary region) and true Hassall's corpuscles. In accordance with the development of the thymic parenchyma, the medullary or basal region may appear either like a true thymic medulla or like a subcapsular region. In the inner thymus, a subcapsular or peripheral "medullary" region and a central area (inverted cortex) show structural features like those of the medullary (basal) and deep cortical regions of the outer thymus, respectively. In addition to the above regions, sometimes there is a lymphomyeloid perithymic infiltration that often extends along connective tissue septa into the perivascular spaces of the gland. Reticuloepithelial, mesenchymal, and unidentified types of stromal cells within the thymus are described. Some erythrocytes, granulocytes, and monocytoid cells are found, but no plasma cells nor erythropoietic foci are evident. The probable significance of these findings is discussed.

The normal human appendix: a light and electron microscopic study.

Human appendices from 3 to 12 years old children were studied by light and electron microscopy. Three morphological zones were determined: sub-epithelial (or lymphoid lamina propria), parafollicular, and follicular. The fine structure of these regions has been studied and discussed with regard to the thymus-dependent and thymus-independent regions of other lymphoid organs. Two types of lymphocytes, 'light' and 'dark', and intermediate forms, were also found. The light ones are the more abundant in the epithelium and within the parafollicular post-capillary venules; they form groups or clusters between epithelial cells, becoming like blast cells and possibly maturing into plasma cells in the sub-epithelial region. Whether light lymphocytes are T or B or both is discussed. The general conclusion is that the human appendix, at least in children, has the characteristics of a well-developed lymphoid organ, suggesting that it has important immunological functions.

Fine structure of canine thymus.

Normal thymuses of young-to-adult healthy dogs have been studied with light and electron microscopy. Two well-defined zones are observed both in the medulla and in the cortex. In the outer cortex including the subcapsular region, reticular cells and mitotic lymphoblasts are more numerous than in the inner cortex, whereas in the central portion of the medulla the small proportion of free lymphoid cells is more evident than in the outer medulla. Reticular cells can be classified into two main groups according to some morphologic features: epithelial and mesenchymal. Epithelial reticular cells seems to undergo a gradual transformation from the subcapsular region to the medulla, and finally they may become heterogeneous Hassall corpuscles. Mesenchymal reticular cells are represented by macrophages and dendritic-like cells. The latter cells are located in the inner medulla and fill the intercellular spaces with their long cytoplasmic processes. In some occasions these processes appear degenerated and plasma cells and eosinophilic leucocytes are found. This fact suggests different functional stages and a possible participation of the normal thymic medulla of the adult dog as a peripheral lymphoid organ.