Sites of synthesis and localization of IgE in rats infested with Nippostrongylus brasiliensis

The tissue and cellular localization of IgE has been studied in normal rats and rats infested with the enteric parasite, Nippostrongylus brasiliensis. The results of the study do not support the suggestion that IgE is a secretory immunoglobulin with a physiology analogous to that of IgA. The lamina propria of the small intestine and the colonic and pulmonary mucosal surfaces contain numerous anti-IgE-binding cells, but these have been shown to be mast cells and not plasma cells. The major sites of IgE synthesis were the regional lymph nodes of the small intestine and the lungs, which contained large numbers of IgE-secreting plasma cells. Smaller numbers of IgE-secreting plasma cells were also found in peripheral lymph nodes, some of which were distant from tissues known to have direct contact with either larvae or adult worms. Peyer's patches, the intrapulmonary lymphoid tissue and the spleen contained few, if any, IgE-secreting plasma cells. The significance of the IgE which was readily demonstrated in germinal centres of Peyer's patches and several lymph nodes is not known. In contrast to infested animals, the lymphoid organs of normal rats rarely contained any IgE-containing cells. Thoracic duct lymph from infested animals contained only few IgE-containing large lymphocytes, similar in number to cells containing IgM or IgG but only 1/50 as many as those containing IgA. An unexpected observation was that mast cells in mucosal organs appear to contain intracellular IgE, differing in this respect from connective tissue mast cells. Mast cells lying between epithelial cells, the 'globule leucocytes', also appear to contain intracellular IgE and it is suggested that such cells may be responsible for the presence of IgE in exocrine secretions. This study highlights the need for careful identification of cells appearing to contain IgE and suggests reasons for the widely differing reports of the numbers of IgE-secreting plasma cells in human intestinal biopsies.

Vascular endothelial markers of the human thoracic duct and lacteal

Factor VIII-related antigen (F8) and Ulex europaeus lectin (UEL) are accepted markers for human blood vessel endothelium. However, disagreement exists as to whether lymphatic vessels stain for F8, and accordingly this study was undertaken to address this issue. Moreover, another vascular endothelial marker, angiotensin converting enzyme (ACE) was also examined in lymphatics. Segments of human thoracic duct and portions of small bowel containing lacteals with post-mortem intervals of less than 15 hours, were removed at autopsy and fixed in B5 or formalin. The specimens were processed routinely and sections examined by indirect immunohistochemical techniques for F8 (Dako Corp.), ACE and for UEL (EY Lab). F8, UEL, and ACE positivity was uniformly found in thoracic ducts and lacteals; however, the staining intensity was less in lymphatic vessels with F8 and UEL than with comparable arteries or veins. ACE staining intensity, on the other hand, was similar in blood vessels and lymphatics. Both formalin and B5 fixation preserved antigenicity; however, background staining was greater with B5 fixation whereas tissue staining was slightly more intense with formalin fixation.

Lymphoid-specific antigen: distribution and behaviour

The distribution of a lymphoid-specific antigen has been studied by immunofluorescence in the thymus and other lymphoid organs of the rat and in the thymuses of other vertebrate species. It was demonstrable in all rat lymphocytes except those of the bone marrow. The thymic lymphocytes of all warm-blooded vertebrates also reacted with the lymphoid-specific serum. Plasma cells in antigenically stimulated lymph nodes did not seem to possess the antigen but similar cells appearing in lymph nodes of rats which had been irradiated and injected with marrow cells of the same strain showed a strong reaction with the antiserum. The antigen is depleted in human and murine leukaemic lymphocytes. X-irradiation did not appear to affect the antigen significantly in cells surviving the treatment.

Studies on lymph humoral factor. Evidence for a lymphocytopoietic factor in rat thoracic duct lymph

Normal rats were injected with the partially purified material extracted from the thoracic duct lymph which was collected from normal syngeneic rats. The cellular changes in the peripheral lymphoid tissues and thymus were examined cytologically and histologically. The intravenous injection of the lymph extract into normal syngeneic rats resulted in increase in weight of lymphoid tissues. Histologically, a massive proliferation of large pyroninophilic lymphoid cells and an increase in mitotic index was detected predominantly in the thymus-dependent areas and thymic cortex. In spleens from rats injected with lymph extract, the marginal zone bridging channel was shown as one route for the translocation or mobilization of newly borne lymphoid cells to the venous circulation. Similar lymphocytopoietic activity, but to a lesser extent than lymph extract, was also detected in lymph plasma, serum and serum extract. The lymph extract was shown to be non-immunogenic in syngeneic rats. It is suggested that the effects of the lymph extract on lymphoid cell proliferation are due to the presence of a lymphocytopoietic factor in body fluid, particularly in the lymph.

A search for an enriched source of polymeric IgA in human thoracic duct lymph, portal vein blood and aortic blood

Because human bile contains a lot of secretory IgA, it has been suspected that the human liver, like rat liver, transfers polymeric IgA from plasma to bile. Hence, a rich source of polymeric IgA might enter the general circulation of man. We examined human thoracic duct lymph, portal vein blood and aortic blood for content and molecular size of IgA. None of the fluids was found to have either a higher total concentration of IgA or a higher proportion of polymeric IgA than that found in peripheral venous blood. It is possible that hepatic clearance of plasma IgA does not occur in man to the extent that it does in the rat, and a relatively larger proportion of human biliary IgA might originate from synthesis in hepatobiliary tissues.

Cellular dissemination of priming for a mucosal immune response to cholera toxin in rats

Using CT as the test antigen, we sought 1) to learn whether primary immunization at 1 mucosal site caused priming of distant nonstimulated mucosae, 2) to study the role of migrating memory cells in the dissemination of mucosal priming, and 3) to compare disseminated priming with priming that occurs at the site of initial immunization. CT given i.c. or i.d. caused priming in tracheal and nonexposed enteric mucosae; i.t. immunization, however, did not cause detectable enteric priming. Adoptive transfer of immune TDLs showed that priming was conveyed by migrating memory cells. These appeared to be of 2 types: those that recirculated briefly before settling in MALT, and those that continued to recirculate until recruited by antigen to the site of mucosal challenge. Both types were required for secondary responses at mucosae distant from the site of priming. The time-course of disseminated mucosal priming resembled that of priming at the site of initial CT exposure, both lasting at least 16 wk. Disseminated priming persisted better in jejunal than tracheal mucosa, suggesting that the subgroup of memory cells that did not continue to recirculate settled preferentially in jejunal MALT. Disseminated priming supported smaller challenge responses than priming at the site of initial CT exposure did, suggesting that sessile memory cells also contributed to the latter process. These observations extend the concept of a "common mucosal immune system" to include cellular dissemination of mucosal priming, but also show quantitative differences between local and disseminated priming that probably reflect the patterns of distribution of migrating and sessile memory cells.

Lymphocyte recognition of lymph node high endothelium. I. Inhibition of in vitro binding by a component of thoracic duct lymph

Rat thoracic duct lymphocytes (TDL) adhere selectively to HEV when overlaid onto glutaraldehyde-fixed frozen sections of lymph node. The results presented demonstrate that thoracic duct lymph contains a factor capable of inhibiting this reaction. A crude preparation of inhibitory factor was isolated from cell and chylomicron-free lymph by (NH4)2SO4 precipitation (60 to 80% saturation). Sephacryl S-200 chromatography revealed 4 major peaks. The inhibitory factor was detected in peak I but not in the others. Similarly peak I but not peak II or III inhibited HEV binding of lymphocytes from lymph nodes and spleen. Peak I emerged near aldolase (m.w. 160,000) and was enriched approximately 50-fold compared to the crude preparation. In addition, experiments employing a rabbit peak I antiserum provided evidence that molecules responsible for inhibition were antigenically related to structures present on TDL but not on thymocytes. It is suggested that inhibitory factor possesses an affinity for lymphocyte binding sites of high endothelium and is derived from shed TDL surface components that play a role in adherence to HEV of lymph nodes.

Kinetics of extravasation and redistribution of IgA-specific antibody-containing cells in the intestine

Double Thiry-Vella loops were prepared in rats, each locally immunized with a different antigen, and the kinetics of appearance in the loops of antibody-containing cells (ACC) specific for each antigen was recorded. The results confirm, under more rigorously controlled conditions, the conclusions of previous work that the initial appearance of IgA lymphoblasts in the intestinal lamina propria occurs independently of antigen. In addition, these findings are extended by demonstrating 1) that there is no specialized site within the intestinal lamina propria for ACC to enter the tissue; 2) that in immunized intestine, specific ACC progressively accumulate around the crypt regions; and 3) that a proportion of this specific accumulation can be accounted for by ACC proliferation within the lamina propria.

The effects of interferon on the recirculation of lymphocytes in the rat

Lymphocytes from the thoracic duct (TDL) were incubated with interferon (IFN) prior to i.v. injection into syngeneic or allogeneic recipient rats. The effect of IFN treatment on the ability of lymphocytes to migrate was studied using 'standard' TDL collected overnight at 4 degrees or an 'optimal' collection of passaged TDL which recirculate with an accelerated tempo (Smith & Ford, 1983). Interferon treatment resulted in an increase in early (30 min) localization of both standard and optimal TDL into lymph nodes. Entry of standard IFN-treated TDL was increased by 91% and 54% in cervical and mesenteric lymph nodes, respectively; increases of 50% and 22% in the same lymph nodes were recorded for optimal IFN-treated TDL. Enhanced entry of standard TDL was contrasted with a reduced ability of IFN-treated TDL to migrate out of lymph nodes; there was a reduced output into the thoracic duct and a surplus of IFN-treated lymphocytes in cervical lymph nodes despite 24 hr continuous thoracic duct drainage. Incubation with interferon did not, however, alter the ability of optimal TDL to reach the thoracic duct rapidly after injection. Allogeneic lymphocytes, which are eliminated soon after injection by an NK-like cytotoxicity, a phenomenon termed ALC, were unaffected by incubation with interferon, thus IFN-treated allogeneic lymphocytes were killed after i.v. injection as rapidly as untreated cells.

Intestinal immunity to Trichinella spiralis is a property of OX8- OX22- T-helper cells that are generated in the intestine

The phenotype of T-helper cells conferring protection against Trichinella spiralis (Ts) was studied using adoptive transfer procedures and T-helper cell subsets isolated by monoclonal antibodies. With these techniques OX8- OX22+ and OX8- OX22- T-helper cell populations were isolated from thoracic duct lymph (TDL) of infected rats three-five-fold more concentrated than in unfractionated lymph. The OX8- OX22- cell subset alone transferred enhanced rejection of adult worms from the intestine. The origin of protective OX8- OX22- cells was examined in mesenteric lymphadenectomized (MX) rats. After MX, protective cells were found in the cell population draining directly from the intestine on Days 2-3 after infection. Protective cells first appeared in the mesenteric lymph node (MLN) and efferent lymph at Day 3. MX rats rejected T. spiralis at the same time as intact controls and showed enhanced rejection when immune TDL were transfused. No evidence was found for a direct role of the MLN in the generation or expression of parasite rejection. Depletion of migrating OX8- OX22- blast cells by 48-hr drainage of TDL did not influence the expression of an anamnestic response to challenge infection. This suggests that an intestinally resident cell population has a substantial role in mediating primary worm rejection and anamnestic immunity. Day 2 OX8- OX22- cells from MX rats proliferated in response to the presentation of adult and muscle larvae antigens in vitro. We conclude that protection resides in the OX8- OX22- T-helper cell subset that is produced and functions in the intestine.

Are Actinomyces viscosus antigens B cell mitogens?

An extracellular heteroglycan (ECHG) and a sonicated cell supernatant (SCS) of Actinomyces viscosus Ny 1 induced strong lymphocyte proliferation. This was shown with spleen and thoracic duct cells form germfree rats and confirmed with cells from conventional "nude" mouse spleens. Spleen cells developed direct plaque-forming cells against densely coupled TNP-SRBC. The mitogenic property of ECHG was diminished considerably after mild alkaline hydrolysis for lymphocytes form rat spleens and was totally abolished for cells from "nude" mouse spleens. These results suggest that ECHG and SCS have B cell mitogenicity.

Inhibition of influenza-immune T cell effector function by virus-specific hybridoma antibody

The in vitro activity of influenza-specific cytotoxic T cells can be inhibited by incubation of the target cells with monoclonal anti-influenza antibodies. Hybridoma antibodies that bind to the virus HA inhibit the cytotoxic activity of TDL for the virus-infected target by as much as 80%, whereas these same antibodies never reduce splenic T cell function by more than 40%. This reflects the fact that TDL from anti-influenza strain A/WSN/33 (HON1) are highly subtype-specific, whereas splenic effector cells from the same mice are cross-reactive for target cells infected with heterologous influenza A viruses. These findings are discussed in the light of previous failures to block virus-immune T cell effector function with heterogeneous antisera produced in vivo, and are considered to favor the idea that at least some of the "virus-immune" T cells are indeed recognizing viral antigens.