Relation between langerhans cells, veiled cells, and interdigitating cells.

Tissue macrophages are bone marrow derived mononuclear cells which play an important role in the immune response, especially as antigen presenting cells. They comprise a heterogeneous population of cells with phagocytic activity. On morphological functional and cytochemical criteria it is likely that the Langerhans cell (LC) in the epidermis, the veiled cell (VC) in the afferent lymph and the interdigitating cell (IDC) in the thymus dependent area of peripheral lymphoid organs and the thymus medulla belong to a subpopulation of the macrophages. They are low phagocytic, Ia positive and are highly immunogenic. VC and IDC may contain Birbeck granules, the characteristic organelles of the LC, suggesting a relationship between these cell types. An epithelial micro-environment as present in the skin epidermis and the thymus is necessary for the induction of these granules, which appear to have no immunological significance. In a scheme the development from monocyte into LC or into VC and subsequently IDC is postulated. Probably VC transport antigen from the skin area via the afferent lymphatics into the draining lymph node. In the thymus dependent area of this organ they present this antigen to T cells and mature into IDC. IDC in the medullary area of the thymus may also be involved in antigen presentation to immunocompetent T cells. However, in this central lymphoid organ a function in instruction of helper T cells may not be excluded.

Ultrastructural and electrophysiologic changes of experimental acute cardiac lymphostasis.

Experimental impairment of cardia lymph flow in dogs produced histologic and electrophysiologic changes in the heart. Interstitial edema, lipid swelling of myofibrils, dilatation of lymph vessels, and fibrinoid degeneration of small coronary arteries occurred in and near the sinus node and the atrioventricular conduction system. On electrical stimulation of the heart, significant shortening of the atrial and ventricular effective refractory periods, increases in the sinus node recovery time and in the atrioventricular conduction time, and ventricular extrasystoles and ventricular fibrillation were observed. Many of these EKG changes are similar to those observed in sick sinus syndrome in man. An attempt was made to create dynamic lymphatic insufficiency by rapid electrical stimulation of the heart. EKG abnormalities observed in these cases could be prevented by intravenous injection of calcium dobesilate.

[Ultrastructural characteristics of virus-producing lymphocytes in bovine leukemia]. / Ul'trastrukturnaia kharakteristika virusprodutsiruiushchikh limfotsitov pri leikoze krupnogo rogatogo skota.

The ultrastructure of peripheral lymphocytes and lymph was examined in 35 head of cattle in health and chronic lymphoid leukemia. In the latter, ultrastructural alterations were detected in the nuclei and cytoplasmic organelles. The alterations appeared as Golgi apparatus hypertrophy, mitochondrial polymorphism, myelinoid formations. There were nuclear pockets, invaginations in the nuclei of leukemic lymphocytes. A correlation was established between the number of cells having nuclear pockets and the virus production of lymphoid cells in chronic lymphoid leukemia. There is evidence that the existence of nuclear pockets along with other indicators may be useful in assessing the development of leukemias in cattle. The morphogenesis of bovine leukemia virus is presented.

Studies of efferent lymph cells from nodes stimulated with oxazolone.

Efferent lymph from nodes regional to areas of skin that had been treated with solutions of oxazolone in acetone was collected from unanaesthetized sheep. The application of 5% solutions of oxazolone to unsensitized sheep caused no signs of acute inflammation or 'shut-down' of lymphocyte traffic; none the less, normal immune responses ensued so that immunoblasts, some containing immunoglobulin, were discharged into the lymph together with specific humoral antibodies. When previously sensitized sheep were challenged with 2.5% solutions of oxazolone the vigorous secondary responses were heralded by Arthus reactions, induced presumably by pre-existing antibodies, which were mainly of the IgG class. A similar sequence of events occurred in a thymus-deprived sheep which had undergone intra-uterine thymectomy at 60 days of gestation. Repeated applications of oxazolone to normal sheep did not exhaust or inhibit the characteristic changes in the flow and composition of the lymph. When immunoblasts from efferent lymph were radiolabeled with 125I-UdR and returned intravenously to the sheep they showed no significant tendency to localize either specifically or non-specifically in areas of skin that had been treated with contact-sensitizing chemicals.