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Exposure of the flank of mice to either oxazolone or trinitrochlorobenzene (TNCB) 5 days prior to the application of oxazolone on the ear resulted in a reduced capacity of oxazolone-induced draining lymph node cells to express IL-2 receptors, produce IL-2, protein, RNA and DNA. However, histological examination of the draining lymph node suggest that antigen-specific and antigen-non-specific influences differ with respect to the frequency of pyroninophilic cells. Pre-exposure to oxazolone suppressed the number of oxazolone-induced pyroninophilic T cell blasts, whereas draining lymph nodes from TNCB-pretreated mice contained significantly more pyroninophilic cells than from oxazolone-pretreated mice. However, the majority of these cells were incorporating little or no thymidine. Thus exposure to certain contact sensitizers induces at least two systemic control mechanisms which serve to regulate subsequent lymphoproliferative responses. These mechanisms appear to exert their influences at different stages of in-vivo T cell activation.

Granulomas which develop in draining lymph nodes, following the intradermal injection of cobalt-irradiated Mycobacterium leprae into the ear of the guinea pig 2 and 5 weeks earlier, were studied in animals which had been presensitized with BCG vaccine or M. leprae and compared with granulomas that developed in previously unsensitized guinea pigs. Presensitization with mycobacteria accelerated the development of the granulomas. Granulomas in previously unsensitized guinea pigs were found ultrastructurally to contain phagocytosing macrophages similar to those in lepromatous leprosy, and M. leprae presensitization did not alter the type of granuloma found. Those in BCG-presensitized guinea pigs contained secretory epithelioid cells with rough endoplasmic reticulum similar to those found in borderline tuberculoid leprosy or reversal reactions. The significance of these findings in relation to the current use of vaccines in leprosy is discussed.

A study was made of mycobacterial-induced granulomas in guinea-pig lymph nodes. Live BCG (Pasteur) induced a granuloma containing epithelioid cells while Cobalt irradiated Mycobacterium leprae induced a granuloma comprised of phagocytic macrophages. The granulomas were quantitated by measurement of lymph node weight and the areas of infiltration in histological sections. The time course of granuloma formation induced by Co-irradiated M. leprae was veary different from the time course of the granuloma formation induced by BCG. Collagen synthesis assessed by incorporation of 14C-proline into collagenase sensitive protein was greater in lymph nodes draining the site of injection of Co-irradiated BCG than those draining the site of injection of Co-irradiated M. leprae during the first 10 weeks. Collagen synthesis was delayed in the nodes from animals injected with live BCG for at least 10 weeks. Single cell suspensions of draining lymph nodes containing granulomas consisted of lymphocytes and large cells (epithelioid cells and macrophages). A high proportion of the large cells were found to be non-adherent in the live BCG-induced epithelioid cell granuloma. In contrast, M. leprae-induced granulomas contained a high percentage of adherent large cells. In both the granulomas, the majority of large cells were esterase positive and showed the presence of fibronectin. Most of the large cells in the granulomas did not carry receptors for the Fc component of IgG or the C3 component of complement and did not exhibit peroxidase activity.

In mice depleted of lymphocytes by thymectomy and cyclophosphamide treatment the popliteal lymph nodes showed macrophages, fibroblasts, endothelial cells and a heterogeneous group of cells here described as reticulum cells. Some of these both within and outside the germinal centres had fine long processes, i.e., were dendritic, and some had deep cytoplasmic invagination. Interdigitating cells were not a feature of the nodes and there was little evidence of migration of cells through post-capillary venules.

A systematic ultrastructural study has been performed of the mononuclear phagocytes in granulomas induced by different types of mycobacteria, e.g. live BCG (Pasteur), irradiated M. leprae and irradiated BCG (Pasteur) in guinea pig lymph nodes. Live BCG (Pasteur) induces a granuloma which peaks at 2-3 weeks and by light microscopy, a large number of the infiltrating cells have the appearance of epithelioid cells. Ultrastructurally a large proportion of these cells have a distinct appearance. They are characterised by the presence of very large nuclei, and prominent nucleoli, paucity of cytoplasmic organelles and swollen rough endoplasmic reticulum. Cells from 2 week granulomas induced by live M. kansasii and BCG (Glaxo), has a similar ultrastructural appearance. BCG (Pasteur) granulomas slowly resolved and by light and electron microscopy fibrosis and collagen deposition was seen by 7 weeks and was very extensive in some nodes at 10 weeks. The nodes from M leprae injected animals showed peak infiltration at 5 weeks and by light microscopy the infiltrating cell population was more mixed, with most of the cells having a macrophage appearance. Electron-microscopy showed these infiltrating cells to be mainly activated macrophages, containing phagocytosed organisms. Nodes from irradiated BCG (Pasteur) injected animals had peak infiltration at 1 week. The light and electron microscopic appearance showed areas consisting mainly of fibroblasts and mononuclear phagocytes. Thus, the granulomas induced by M. leprae are very different from those induced by BCG in the guinea pig. It is suggested that lymph nodes draining areas of local injection of BCG and irradiated M. leprae could respectively form a good model in the guinea pig for cellular and biochemical studies of the granulomas of tuberculoid and lepromatous leprosy.

Dendritic cells were enriched from guinea pig auricular lymph nodes containing Mycobacterium leprae induced granulomas by immunomagnetic depletion of other cells. These cells were strongly positive for major histocompatibility complex class II antigens and labelled with an antidendritic cell monoclonal antibody, but not with an antimacrophage antibody. Interdigitating dendritic cells were identified in the granulomatous lymph node by staining with the antidendritic cell antibody and by transmission electron microscopy. When cultured in vitro with purified T lymphocytes, these cells acted as accessory cells for both purified protein derivative and concanavalin A induced proliferation. Although previous studies have shown that macrophages from these lymph nodes do not act as accessory cells, the present results indicate that dendritic cells from M. leprae granuloma containing lymph nodes may act as antigen-presenting cells.

An assessment of T-lymphocyte proliferation and lymph node weight is proposed as a predictive test for contact sensitizers of industrial origin. Data are presented showing increased T-lymphocyte proliferation following epicutaneous application of a variety of industrially important acrylate-like chemicals which appear to correlate well with their ability to sensitize in the guinea pig. These data were compared with those obtained after application of 2,4-dinitro-1-fluorobenzene (DNFB) a strong sensitizer, and 2,4-dinitrothiocyanatebenzene (DNTB) a nonsensitizer when given epicutaneously. It is suggested that this quantitative approach, in parallel with a simple one-dose immunization, may provide a better picture of sensitization potential than the longer multidose immunizations currently in use.

This memorandum proposes a standardized system of reporting the histology of human lymph nodes based on commonly used simple staining techniques. The purpose is to provide a uniform, internationally acceptable system by which the histological structure of lymph nodes can be correlated with other parameters of immunological status. The proposed protocols are intended to provide information that is not available in conventional written reports that use such terms as ;hyperplasia' or ;nonspecific lymphadenitis'.

This Memorandum proposes a standardized system of reporting the histology of human lymph nodes based on commonly used simple staining techniques. The purpose is to provide a uniform, internationally acceptable system by which the histological structure of lymph nodes can be correlated with other parameters of immunological status. The proposed protocols are intended to provide information that is not available in conventional written reports, that use such terms as "hyperplasia" or "nonspecific lymphadenitis".

Antibodies produced in rabbits against mouse brain are able to react with the majority of lymph node and spleen murine lymphocytes, as demonstrated by indirect immunofluorescence. Cells stained by a suitably absorbed rabbit anti-mouse brain serum showed various degrees of fluorescence, from bright fluorescent rings to a few speckles per cell; lymphocytes from the spleen of deprived mice (B mice) predominantly stained in small caps. Double labelling experiments in which B cells were identified by their ‘easily detectable’ surface immunoglobulin revealed that a great proportion of these cells had two overlapping caps, a large one formed by the anti-immunoglobulin serum and a small one formed by the anti-brain serum. Up to 10 per cent of these spleen B cells, however, appeared as strongly fluorescent as T cells, with the suitably absorbed heterologous anti-brain serum. No anti-immunoglobulin activity was detected in this serum. It is therefore suggested that some B cells may bear on their surfaces a θ or θ-related antigen similar to that on T cells. [ABSTRACT FROM AUTHOR]

Epicutaneous exposure of mice to the contact sensitizing chemicals 4-ethoxymethylene-2-phenyl- oxazol-5-one (oxazolone) and 24,6-trinitrochlorobenzene (picryl chloride) causes an inhibition of proliferative responses induced following subsequent topical challenge. The effects on lymphocyte proliferation comprise both transient antigen non-specific and more persistent hapten-specific mechanisms. Pretreatment of mice with one chemical 5 days prior to sensitization with a second, at which time antigen non-specific influences on proliferative responses are manifest, results in depression of contact sensitization as measured by changes in ear thickness following challenge. If, however, the period between pretreatment and sensitization is extended the inhibition of contact sensitization disappears in parallel with a decline in the antigen non-specific depression of lymph node cell proliferation. These data reveal that there exist two homeostatic mechanisms which control proliferation in response to challenge with at least some antigens, and that the extent of lymphocyte proliferation directly influences the degree of contact sensitization achieved. Moreover these results demonstrate that, in some instances at least, competition between antigens may be a function of immunoregulatory influences on lymphocyte proliferation. [ABSTRACT FROM AUTHOR]

The effect of a single injection of 300 mg/Kg on the lymphoid cells of normal mice has been studied. The proportions of θ-positive cells in the thymus, lymph nodes and spleen were examined in vitro using a Trypan Blue exclusion cytotoxicity test. Two anti-θ sera of different titre were employed in an attempt to evaluate changes in θ-antigenicity of these cells following azathioprine treatment. In the thymus the drug was found to deplete a particular population of cortical thymocytes without affecting the hydrocortisone-resistant cells. The ability of azathioprine-resistant thymocytes to absorb out the cytotoxic capacity of both antisera was not better than that of hydrocortisone-resistant thymocytes. This result was taken to indicate that, following azathioprine, the residual cells had a decreased frequency of the θ antigen and were in this respect more like hydrocortisone-resistant cells. It is also postulated that the two antisera were of different avid- A decrease in antigenicity was also seen in lymph node cell populations from azathioprine-treated animals. It is therefore suggested that azathioprine given in heavy doses might have at least two effects on lymphoid cells: (i) it depletes certain populations; and (ii) it decreases the θ-antigenicity of others. [ABSTRACT FROM AUTHOR]

Selective depletion of lymphocytes from the lymph follicles and corticomedullary junction in lymph nodes and equivalent non thymus dependent areas of the spleen can be produced by cyclophosphamide (CY) (300 mg/kg) in the mouse and guinea-pig. Despite three such injections on alternate days, thymus dependent areas still contained lymphocytes. Total depletion of lymphocytes from lymph nodes and spleen was produced by combining neonatal thymectomy in the mouse or ALS treatment in the guinea-pig with CY. CY produced depletion of lymphocytes in the cortex of the thymus before the medulla. Maximal depletion occurred at 3 days and in surviving animals repopulation was evident by 7 days at the cortico-medullary junction only. Lymph follicles were found in lymph nodes of neonatally thymectomized CY treated mice following repopulation with bone marrow. These findings suggest that the lymphocytes of the lymph follicles are derived from a population of rapidly dividing cells, part of which at least can be found in the bone marrow. [ABSTRACT FROM AUTHOR]

The effect of anti-thymocyte serum, anti-lymph node cell serum and anti-lymph node permeability factor serum have been compared on the peripheral manifestation of contact hypersensitivity in the guinea-pig and certain models of acute inflammation in the guinea-pig and the rat. Anti-lymph node permeability factor serum has a similar effect to the anti-lymphocyte sera on contact hypersensitivity. However, its effect on non-specific inflammation is very much less. The mechanism of action of anti-lymphocyte sera on the models of non-specific inflammation has been studied more thoroughly to attempt to work out the level at which inhibition occurs. The central effect of these different antisera on lymph nodes reacting during the development of sensitivity to a chemical sensitizer has also been studied. Anti- serum prepared against cells derived from lymph nodes has the same specific effect on the thymus-dependent area of the lymph node as antiserum prepared against cells derived from the thymus. These changes are compared with those produced by anti-lymph node permeability factor serum and anti-epidermal cell serum. [ABSTRACT FROM AUTHOR]

Peritoneal exudate lymphocytes (PEL), purified on glass beads and lymph node (LN) cells from guinea-pigs immunized with tubercle bacilli were cultured for 24 hours, in serum-free medium, without and with various concentrations of Tuberculin PPD. Supernatants obtained from cultures with 10 μg PPD/107 lymphocytes provoked an intense inflammatory reaction, when injected into the skin of normal guinea- pigs. PEL were more active than LN cells from the same animals. The reaction was characterized by erythema and induration, with a peak between 3 and 6 hours and histologically a mixed polymorphonuclear-mononuclear infiltrate in the dermis was seen. When fractionated on Sephadex G-200, skin activity of both PEL and LN supernatants was concentrated in a peak corresponding to the molecular weight of serum albumin, while in LN material some activity was also present in a small molecular weight peak. The active material could be separated from albumin by chromatography on DEAE-cellulose. Immunoelectrophoretic analysis of skin reactive peaks detected a slow α-globulin in both PEL and LN supernatants. PPD in the form of a complex with a protein precipitated by anti-γG antiserum, was detected in the skin-active Sephadex peak III of LN supernatants, by radio- immunoelectrophoresis. Skin activity was precipitated with ammonium sulphate at 66 per cent saturation and was destroyed by pepsin treatment. Formation of the skin-active material was depressed by Puromycin and Actinomycin-D and the development of skin inflammation was suppressed by pretreatment of the recipient with anti-lymph node extract serum. Evidence for antigen induced specific synthesis and release of an α-globulin in PEL and LN cultures was found but its relation to the skin active material is unknown. [ABSTRACT FROM AUTHOR]