Histochemical study on human germinal centre, mantle-zone and extra-follicular area lymphoid cell subpopulations. Immunological and cytochemical correlations with lymphomatous cells, peripheral normal and leukemic lymphocytes

[Histochemical and immunohistochemical study of the lymphoid tissue of swine: lymphatic ganglia, spleen and thymus]

Immunohistological (S-100, cIg) and enzyme histochemical (ANAE/ANBE, beta-glu, ATPase, AcP) investigations were carried out to identify lymphocyte and reticular cell subpopulations "in situ", in pig lymphoid tissue (lymph node, spleen, and thymus) of a 6 months old group, and a 6-9 days old one. By means of immunohistological techniques, in the 6 month old pigs we could detect S-100 protein (PAP), chiefly in T-areas lymphocytes, but we also found some S-100 positive lymphocytes in spleen follicles. Also S-100 protein were detected at Follicular Dendritic Cells (FDC) in lymph node and spleen; and Reticular Fibroblastic Cells (RFC) only in the first one. Finally, S-100 were noted in Hassall corpuscles (thymus), nervous fibres, and endothelial cells too. Using PAP (IgG, IgM) and IPI (IgA) techniques we could detect lymphocyte cytoplasmatic surface immunoglobulins (cIg) in lymphocytes, lymphoblastoid and plasmacytoid cells in nearly all tissue compartments. By means of histochemical techniques we could identify T-area lymphocytes ANAE/ANBE and beta-glu positives (cytoplasmatic spots) and B-area lymphocytes ATPase positive; macrophages, and polymorphonuclear eosinophiles PHNE being ANAE/ANBE and beta-glu positives (diffuse cytoplasmic stain); and Hassall corpuscles ANAE/ANBE and AcP positives. Concerning to reticular cells, we found FDC and RFC in lymphoid follicles, and Interdigitating Reticular Cells (IDC) in lymphoid diffuse tissue, with enzyme activity (all the enzymes studied) in nearly all the cases. In piglets, the immunohistological and histochemical pattern was nearly the same.

Mg2+-dependent adenosine triphosphatase: an enzyme marker for ovine T lymphocytes

Sheep T lymphocytes showed a cell surface magnesium-dependent adenosine triphosphatase (Mg2+-ATPase) reaction, which is reported to be characteristic of human B lymphocytes. In cryostat sections of lymph nodes, spleen and thymus, Mg2+-ATPase positive regions closely matched those labelled by sheep pan T monoclonal antibodies (Moab). An Mg2+-ATPase reaction was also found in fibroblastic recticulum cells of T cell regions in lymph nodes. Double labelling of cells from peripheral blood and peripheral lymph for Mg2+-ATPase and the pan T marker showed that 78% of the lymphocytes were positive for both of these markers. In cell suspensions enriched for B lymphocytes the percentage of cells positively labelled was decreased to 37%. Samples of each cell population which were labelled with a pan T Moab and analysed by flow microfluorometry revealed T cell levels which were not significantly different from those obtained by histochemical or immunohistochemical techniques. Less than 1% of lymphocytes positive for heavy and light chains of immunoglobulin (Ig) G were labelled with Mg2+-ATPase. Veiled cells in lymph and monocytes showed a cytoplasmic Mg2+-ATPase reaction.

Immunoarchitecture of the "pseudofollicles" of well-differentiated (small) lymphocytic lymphoma: a comparison with true follicles

Some human malignant lymphomas of the B-cell type have morphologic and immunologic similarities to follicles seen in nonneoplastic reactive lymph nodes. In contrast, a peculiar, vaguely nodular pattern of growth called "pseudonodules" or "pseudofollicular proliferation centers," which is morphologically distinguishable from "true" follicles, is seen in malignant lymphoma, well-differentiated (small) lymphocytic type (WDL). To characterize the cellular components of "pseudofollicles," we undertook a detailed, comparative immunohistologic study of the architectural relationship and distribution of T cells, B cells, and follicular dendritic reticulum cells (DRCs) in reactive follicles, neoplastic follicles, and pseudofollicles. We report several observations on the presence of DRCs and T-cell subset topography in pseudofollicles. Immunohistologic staining for the C3d complement receptor on DRCs revealed that DRC networks associated with "true" follicles were present in all cases of reactive follicular hyperplasia (RFH) and malignant lymphoma, nodular, poorly differentiated lymphocytic type (PDL) studied. Surprisingly, DRC networks were also identified in 8 of 23 cases of WDL. Although the size distribution of DRC network diameters was nearly identical in RFH and PDL, the sizes were markedly diminished in WDL. Immunohistologic staining for Leu 3+ and Leu 2+ T-cell subsets confirmed cellular arrangements in RFH and PDL reported by others. In only 2 of 23 cases of WDL could T cells localized to "pseudofollicles" in frozen tissue sections be identified in a nonrandom arrangement.

Relationship between structure and T-lymphocyte maturation in human thymomas. Enzyme histochemical and immunohistological studies

Twenty-six human thymomas were studied in an attempt to correlate their morphological appearance with the type and degree of T-lymphocyte maturation, as determined by acid alpha-naphthyl-acetate esterase (ANAE) activity and immunological analysis. Four normal human thymuses were used for purposes of comparison. Two morphological patterns were identified in the thymomas. The distinction was based largely on similarities between the neoplastic epithelial cells and normal cortical and medullary epithelial cells, and on the relative proportions of epithelial cells and lymphocytes. By these criteria "medullary" and "cortical" patterns were identified. In several thymomas both patterns were present in the same tumor ("mixed-type pattern"), producing alternating dark cortical-like areas and lighter foci of medullary differentiation. A good correlation was found between the two patterns and the phenotype of the T-associated lymphoid component. ANAE activity, which was completely lacking in normal cortical thymocytes, was almost absent in the phenotypically immature T-cells of cortical-type thymomas. By contrast, in the medullary-type thymomas, T-cells showed immunological features in common with medullary thymocytes. This was characterized by strong ANAE activity in the majority of cells with a staining pattern corresponding to that of peripheral T-lymphocytes. In addition, most of the proliferating epithelial cells in medullary-type thymomas stained strongly with anti-cytokeratin and anti-epidermal-type keratin antisera. In the mixed-type thymomas the epithelial cell morphology and the immunohistochemical and enzymic features of the T-cells were found to be closely related to the respective cortical--or medullary-like areas. It was concluded that the various characteristics of normal thymic cortex and medulla studied are also present in thymomas. In particular, in medullar-type thymomas the presence of many of the features of normal thymic medulla, such as a squamous cell component, macrophages and interdigitating reticulum cells, may constitute a microenvironment which operates actively in T-cell education. This may account for the functional activities, characteristic of peripheral T-lymphocytes, which T-lymphocytes attain in these thymomas.

Immunohistochemical and enzyme histochemical contributions to the problem concerning the role of the thymus in the pathogenesis of myasthenia gravis

Normal fetal and postnatal thymuses, as well as thymuses from patients with myasthenia gravis (MG), were investigated by immunohistochemical and enzyme histochemical techniques and their morphology reviewed. Intrathymic B-cells, detected by ATPase activity, were found to be markedly increased in number in MG thymuses. They were scattered in the medulla and accumulated around the junctional and medullary vessels and Hassall's corpuscles (HCs). Large epithelial cells, singly or within HCs, were found to be unevenly distributed in the medulla of all the thymuses examined. The striated muscle-like nature of some of these cells was revealed by the presence of myoglobin in their cytoplasm. In myasthenics these cells and small developing HCs characteristically surrounded lymph follicles and were in direct contact with the expanded cap of the follicle mantle, without interposition of reticulin fibres. The close association of immune reactive foci (lymphoid follicles, junctional and medullary vessels, and HCs) with structures involved in autoimmune responses in the thymus (muscle-like and true myoid cells, HCs) strongly suggests that the autoimmune reactions against AChR (acetylcholine receptor) and other muscular components, which constitute the basic defects in myasthenia gravis, may begin in the thymus.