Paracortex Of Lymph Nodes Research Articles

The migration of lymphocytes across vascular endothelium

According to Morris and his colleagues the migration of lymphocytes from the blood into inflammatory sites is a morphologically similar process to the large scale migration of lymphocytes into the paracortex of lymph-nodes which occurs under normal conditions. Little is known of the nature of the selective interaction between lymphocytes and specialized endothelial cells although several investigators have tested the migratory properties of lymphocytes which have been treated in vitro with enzymes or lectins and injected i.v. Such results are difficult to interpret because decreased lymph-node localization may be secondary to increased localization elsewhere. To overcome these difficulties the mesenteric lymph-node chain of the rat was perfused at 37 degrees C for 30-60 minutes with rat serum at 0.33 ml/min. When labelled lymphocytes were added to the perfusate the uptake of cells into the lymph-nodes was 2.13 +/- 0.63% of the number of which had passed through the preparation and this fraction was independent of the concentration in the perfusate over a wide range. No release of lymphocytes from the isolated node into the perfusate could be detected. Neuraminidase treated lymphocytes localized in the perfused lymph-node at least as well as did untreated lymphocytes in contrast to their deficient lymph-node localization following i.v. injection into intact recipients as originally found by Gesner. Other evidence has been found that the primary effect of neuraminidase treatment is to increase hepatic localization. Large lymphocytes migrate into the isolated node more readily than do small lymphocytes which is also in contrast to results in intact recipients. The migration of lymphocytes treated with trypsin or concanavalin A has also been studied.

Antigenic relationship between medullary thymocytes and a subpopulation of peripheral T cells in the rat: Description of a masked antigen

Using differentially absorbed rabbit antisera to rat thoracic duct cells, an antigen is described which normally is expressed on the surface of T cells in thoracic duct lymph and lymph node, but which exists in a masked form on medullary thymocytes and apparently not at all on cortical thymocytes. This antigen is termed the rat masked thymocyte antigen (RMTA). RMTA on medullary thymocytes can be unmasked mechanically by sectioning in a cryostat or enzymatically by treating with neuraminidase. Trypsin destroys or removes RMTA. Nearly all the T cells in thoracic duct lymph and lymph node are RMTA +, whereas only 58–66% of T cells in spleen are RMTA +. RMTA + T cells, which are cortisone resistant, reside in the paracortex and periarteriolar sheath regions of lymph node and spleen. RMTA − T cells, which are cortisone sensitive, appear to reside in the red pulp of spleen. The results suggest that (i) two antigenically distinct populations of T cells exist in the rat, RMTA + and RMTA − T cells, (ii) medullary thymocytes are the immediate precursors of RMTA + T cells, and (iii) cortical thymocytes may be the immediate precursors of RMTA − cells.

The effect of thymectomy on the lymphoid tissues of the quokka (Setonix brachyurus).

SummaryThe effects of cervical and total thymectomy on the lymphoid tissue of the quokka (Setonix brachyurus) have been investigated. In the first month of life alter cervical thymectomy retardation of the development of lymphoid tissue occurs. Total thymectomy results in the lymphocytic depletion of the paracortex of lymph nodes and the splenic malpighian bodies of pouch young and juveniles. These effects are maximal if cervical thymectomy is performed within the first 5 days of post‐natal life while the time of thoracic thymectomy is less critical.

Experimental listeria monocytogenes-lymphadenitis. Pathohistological observations.

The auricular lymph nodes of SPF guinea pigs were examined light microscopically at various stages (30 min to 14 days) after subcutaneous injection of Listeria monocytogenes. The bacteria entered the lymph node parenchyma through the marginal sinuses and were phagocytosed by polymorphonuclear leukocytes and monocytes at early stages of the infection (30–60 min). Whereas retothelial cells of the sinuses did not phagocytose bacteria, submarginal reticulum cells showed a high bacterium-phagocytosing activity. Starting at 12 hours after inoculation lymphocyte activation occurred in the interfollicular diffuse lymphatic tissue of the cortex and in the paracortex. The activated lymphocytes were released into the sinuses. There was also paracortical distension, which reached its peak on the 6th day of infection. The submarginal area at the junction of the afferent lymphatic with the cortex and the perivascular regions of the lymph node paracortex were the preferred sites of granuloma formation. On the 8th day with a dose of 106 bacteria the macrophages of the granulomas revealed only unidentifiable debris in the cytoplasm, whereas in the earlier lesions a large number of mononuclear phagocytes, especially in the submarginal granulomas, contained many intracytoplasmic listeria. The granulomas gradually became smaller and smaller. With larger infectual doses the process did not subside within the experimental period; the granulomas developed the appearance of “reticulocytare abszedierende Lymphadenitis”.

SKIN GRAFTS IN NUDE MICE

Mice, homozygous for the nu gene (nude mice), have no capacity for rejection of allografts as evidenced by this study of nine different graft‐host combinations. The mice concerned stem from an intermediate stage in a nu gene transfer to three inbred strains (BALB/c, C3H, C57/BL). Mice of each of the three genetic backgrounds accepted skin grafts from three inbred donor strains, differing at the H‐2 locus. A preliminary comparison with a concurrent study of heterografts (rat skin) indicates that allografts are not so readily incorporated, and are more prone to endogenous damage during the take process. This paradoxical observation is discussed at greater length in the subsequent article on heterotransplants in nude mice. After allografting, nude mice display lymphocytosis, and there is lymphoid cell proliferation in the primary follicles of lymph nodes, and increased numbers of mononuclear cells are seen in the paracortex of lymph nodes and in the red pulp of the spleen. No cytotoxic alloantibodies could be demonstrated in serum from the graft bearing nude mice. Thymus grafting confers capacity for allograft rejection.

Anatomical distribution of T and B lymphocytes in the rat. Development of lymphocyte-specific antisera.

A method is described whereby antisera raised in rabbits to rat thoracic duct lymphocytes were made specific for the plasma membrane antigens of T and B lymphocytes. These lymphocyte-specific antisera were used in immunofluorescence assays to study the distribution of B and T cells in lymphocyte containing tissues and body fluids of the rat. Rabbit antirat B-cell serum (ALS(B)) reacted selectively with the surfaces of lymphocytes in the lymphoid follicles of lymph node cortex and in the follicles and marginal zones of splenic white pulp, but not with the surfaces of germinal center cells or plasma cells. An identical pattern of fluorescent staining was obtained with rabbit antirat Ig serum. It was shown by blocking, absorption, and immunoprecipitation studies that ALS(B) was composed in large part of antibodies to rat Ig, but that it contained antibodies to other B-cell antigens as well. Rabbit antirat T-cell serum (ALS(T)) reacted selectively with the surfaces of lymphocytes in the paracortex of lymph node and in the periarteriolar sheath of spleen, and with thymocytes. ALS(T) did not display anti-Ig activity. ALS(T) reacted with approximately 100% thymocytes and with 90% thoracic duct, 80% lymph node, 60% blood, 50% spleen, and 10% bone marrow lymphocytes in suspensions of cells from these sources. ALS(B) reacted with the remainder of the lymphocytes in the suspensions, except for bone marrow in which only 59% of lymphocytes had detectable B- or T-cell surface antigens. The population of T lymphocytes in rat bone marrow was depleted by drainage of lymphocytes from a thoracic duct fistula, thereby establishing their membership in the pool of recirculating T cells. Approximately 14% of lymphocytes issuing from the thoracic duct of TxBM donors reacted with ALS(T). The presence in these animals of a small number of T cells, calculated to be approximately 2% of the normal value, may account for the limited capacity of TxBM rats to respond to antigens that induce a cell-mediated immune response.