Immunohistochemical identification of mastocytes

Antibodies to mastocytes were localized in cells and tissues following formaldehyde or paraformaldehyde fixation and embedding into paraffin or Durcupan ACM, and after chymotrypsin treatment of the sections. Immunomicroscopic examination yielded a more distinct picture of the amount and localization of mastocytes in different tissues.

Germinal centers and the B-cell system. VI. Migration pattern of germinal-center cells of the rabbit appendix

The migration pattern of germinal center cells of the rabbit appendix was studied and compared with that of appendix dome cells, spleen cells, thymus cells and thoracic duct lymphocytes. To discriminate T- and B-cell migration pathways, normal or T-cell-depleted rabbits were used as donors. Cell suspensions were labeled in vitro with 3H-leucine followed by intravenous transfer. The migration of labeled cells in lymphoid organs was studied using autoradiography, particular attention being paid to the spleen of the recipient. B-cells from the appendix dome, spleen and thoracic-duct lymph migrate to primary follicles or the corona of secondary follicles via thymus-dependent areas of peripheral lymphoid organs. In contrast, a B-cell subpopulation from the germinal centers of the appendix migrates to the center of splenic primary follicles and into germinal centers. The migration of germinal center cells to splenic follicle centers is not enhanced by specific antigens. The migration properties of B-cells, possibly changing during differentiation, may be instrumental in the two types of immune reactions, i.e., plasma-cell reaction and germinal-center reaction.

Germinal centres and the B cell system. III. Germinal centre forming capacity of rabbit appendix germinal centre (-derived) cells

Following appendectomy and sublethal (450 rads) whole body X-irradiation, reconstitution with autologous appendix germinal centre cells led to excellent germinal centre formation in the recipient's spleen. Heat killing of the cells to be injected completely abolished this phenomenon. Apparently a suspension of appendix germinal centre cells contains a (sub)populations of cells capable of germinal centre formation (Germinal Centre Precursor Cells). Following whole body X-irradiation while shielding the appendix, germinal centre activity could only be detected after antigenic stimulation in otherwise normally regenerated splenic follicular structures. This suggests that the cell population recently derived from appendix germinal centres is able to function once again as a population of germinal centre precursors.

Germinal centres and the B cell system. IV. Functional characteristics of rabbit appendix germinal centre (-derived) cells

Functional capacities of rabbit appendix germinal centre cells were tested in appendectomized, 450 rads X-irradiated rabbits, reconstituted with autologous appendix germinal centre cells, which are obtained by mechanical separation--"stripping"--of the appendix. For comparison, functional capacities of appendix germinal centre derived cells were tested in rabbits, 450 rads X-irradiated with the appendix shielded. In both types of experimental systems, slow restoration of primary IgM responsiveness to Salmonella Java paratyphi-B (PAR) was observed; in contrast, the capacity for memory cell production (of both mu and gamma-type) to PAR was restored very early in both systems. These results suggest germinal centres to be antigen dependent microenvironments for selective as well as non-selective amplification of immature B cells, which after subsequent maturation become part of the pool of either memory or virgin mature B cells respectively.

Lymphocyte positions in the dome epithelium of the rabbit appendix

The apico-basal distribution of lymphocytes within the epithelium covering the domes of lymphatic tissue in the wall of the rabbit appendix was investigated in single and serial sections stained either for general histology, for cytoplasmic basophilia and acidophilia, or for nonspecific esterase activity. From the base to the summit of a dome, four zones numbered proximo-distally 1-4 were distinguished. Epithelial cells migrate from base to summit, as indicated by mitotic figures in zone 1, the gradual change from cytoplasmic basophilia to acidophilia in zones 2 to 4, and visible extrusion of cells from zone 4 at the summit. Zone 1 was free of lymphocytes. Most of the lymphocytes in zone 2 were intercellular and randomly arranged, but a few in this zone were within tapered epithelial cells modified by a process extending basally to the basement membrane. Small numbers of these tapered epithelial cells also occurred in zone 3. The large clusters of ten to 12 lymphocytes that characterized zone 3 were intercellular and impinged the apical regions of epithelial cells. Serial sections at the level of the distal cluster of zone 3 showed lymphocytes located also more basally, and some of these lymphocytes appeared to be passing through the basement membrane back into the lymphoid tissue of the dome. Epithelium of zone 4 over the distal surface of a dome was largely free of lymphocytes. Apparently most infiltrating lymphocytes form intercellular clusters and then return to the subepithelial lymphatic tissue.

Surface immunoglobulin receptors of rabbit lymphoid cells. Evaluation of fluorescent staining with antibodies to immunoglobulin light chain allotypes

Rabbit lymphoid cells were stained with fluorescein-labelled antiallotype antibodies. The double layer technique was found to be more sensitive than the direct staining. Rabbit B cells are stained only via their surface immunoglobulin (sIg) receptors and not via the receptors for the Fc portion of the IgG. Peritoneal exudate macrophages do not carry sIg receptors and are stained via their Fc receptors. Removal of protein aggregates from the system and use of reagents prepared from F(ab')2 immunoglobulin fragments prevent staining of the macrophages through their Fc receptors. There was a good agreement between the percent of RABELA-positive and sIg-containing spleen cells. In appendix there were approximately 20% more RABELA-positive than sIg-positive cells.

The normal human appendix: a light and electron microscopic study

Human appendices from 3 to 12 years old children were studied by light and electron microscopy. Three morphological zones were determined: sub-epithelial (or lymphoid lamina propria), parafollicular, and follicular. The fine structure of these regions has been studied and discussed with regard to the thymus-dependent and thymus-independent regions of other lymphoid organs. Two types of lymphocytes, 'light' and 'dark', and intermediate forms, were also found. The light ones are the more abundant in the epithelium and within the parafollicular post-capillary venules; they form groups or clusters between epithelial cells, becoming like blast cells and possibly maturing into plasma cells in the sub-epithelial region. Whether light lymphocytes are T or B or both is discussed. The general conclusion is that the human appendix, at least in children, has the characteristics of a well-developed lymphoid organ, suggesting that it has important immunological functions.

[Suppressive effect of autologous thymocytes abolished by prednisolone]

The authors studied the effect of autothymocytes on the hemolysin-producing cells formation in different lymphoid organs of young rabbits. Intravenous injection of thymocytes proved to suppress the formation of antibody-producing cells in the spleen of animals. Prednisolone treatment of thymocytes before their injection cancelled the suppressive effect of autologous thymocytes.

[Characteristics of the lymphoid cells of rabbits]

By means of scanning electron microscopy it has been stated that the thymus gland, spleen, paratracheal lymph node, Peyer's patches and appendix in an intact rabbit of "Shinshilla" strain have T- and B-lymphocytes in different proportion. T-lymphocytes are seen as spherical cells with rough surface, with a few microprocesses, have 3.0 +/- 0.1 mcm--4.7 +/- 0.2 mcm in diameter depending on their location. B-lymphocytes are seen as spherical cells with a considerable amount of microvilli on their surface, have 2.9 +/- 0.1 mcm--4.4 +/- 0.1 mcm in diameter depending also on their location. In the thymus gland, cells with rough surface, a few microprocesses and crater-like hollows prevail. In the spleen and lymph node, most of the cells are of similar diameter and have microvilli on the surface. Lymphoid population in the Peyer's patch and appendix is represented by large cells with microprocesses.

T- and B-cell surface markers on rabbit lymphocytes

Rabbit thymus, appendix, blood and lymph nodes were characterized using immunological tests: rosette-forming ability with homologous or heterologous red blood cells, surface immunoglobulins, analytical cell-electrophoresis, cell refringency and in vitro mitogen responsiveness. The experiments were conducted on normal rabbits and cyclophosphamide-treated rabbits. Moreover, we tried to separate slow and high mobility cells by free-flow electrophoresis into fractions. These experiments suggest that rabbit lymphocyte behaviour is exceptional among mammals in that the majority of their lymphocytes appeared as B cells and that, in comparison with mouse and man, the proportions of these cells are inversed.

Localization of T and B lymphocytes in human adenoid, tonsil, appendix and Peyer's patches

T and B lymphocytes were detected in human adenoid, tonsil, appendix and Peyer's patches by adherence to sheep erythrocytes (E) and human erythrocytes sensitized with antibody and complement (HEAC). The percentages of T lymphocytes in adenoid and tonsil cell suspensions averaged 30.9 +/- 3.4 (S.D.) and 35.8 +/- 6.4 (S.D.). The percentages of B lymphocytes in the same tissues were 42.5 +/- 11.3 (S.D.) and 40.1 +/- 34 (S.D.) respectively. In adenoid and tonsil tissue sections, B lymphocytes were found in the follicles and T lymphocytes were detected around the follicular areas. The predominant cell population in Peyer's patches and appendix sections was constituted by B lymphocytes.

Distribution of T and B lymphocytes in lymphoid tissue of infants and children

Normal lymphoid tissue from children undergoing elective surgery was examined for T and B lymphocyte distribution. Although established for peripheral blood and bone marrow, T and B lymphocyte distributions have not been previously reported for lymph nodes, appendix, thymus, and spleen tissues in children. Thymus-dependent T cells were determined by the sheep erythrocyte rosette technique, and thymus-independent B cells were determined by the fluorescent labeling of surface immunoglobulins A (IgA), G (IgG), and M (IgM). Fifty percent of lymph node cells were either T or B cells; 65% of these cells were T lymphocytes, whereas 58% of B cells were of the IgM subclass. Less than half of the appendix cells were either T or B cells; 47% of these were T lymphocytes, and the remainder B lymphocytes had subclass distribution similar to that of lymph nodes but different from peripheral blood and bone marrow where B cells bearing IgG predominate. Thymus tissue contained 43% T cells and less than 1% B cells, but the spleen was composed largely of B cells, predominantly of the IgM type. Lymphoid tissue from nine children with either inflammatory or neoplastic diseases were studied and included for contrast. This paper establishes relative distribution values for T and B lymphocytes in normal lymphoid tissue and points out the potential use of this technique to quantitate deviations from normal in certain inflammatory and neoplastic diseases.

Cholinesterase activity in some human lymphatic organs

(1) Cholinesterase activity was investigated in some human lymphatic organs (palatine tonsil, 'normal' spleen, 'bilharzial' spleen, thymus, lymph node and appendix) using GOMORI'S modification of KOELLE and FRIEDENWALD'S thiocholine iodide method, hydrolyzing acetylthiocholine iodide and butyrylthiocholine iodide. (a) Acetyl- and butyrylcholinesterases seemed to be different enzymes; but when they have the same pattern of activity, the latter generally offers a weaker reaction. (b) All the lymphatic follicles of the tonsil, those found in the cortex of the cervical lymph nodes as well as those present in the appendix, were stainable with both acetyl- and butyrylcholinesterase. (c) Acetylcholinesterase activity was not demonstrated in the Malpighian bodies of the 'normal' spleen, but the reaction was strongly present in the blood vessels (including the central arterioles) as well as in the capsule and the different components of the trabecular system. (d) In 'bilharzial' splenomegaly a relatively strong activity started to appear in the Malpighian corpuscles, manifested as a brownish precipitate in their centres. Also some patchy positive areas began to make their appearance in the tissue of the red pulp and had a particular arrangement around the Malpighian corpuscules, in such a way as to 'wall them off' from the tissue of the red pulp. (e) In the thymus no acetylcholinesterase activity was encountered, except in Hassal's corpuscles and in the trabeculae between the thymic lobules. (2) The data obtained in this work were discussed in relation to previous works in other laboratories and it seems that a species difference exists. (3) Cholinesterases may be present in the lymphatic tissue in order to get rid of some potentially toxic esters resulting from the necrobiotic phenomena accompanying the high mitotic activity found especially in the germinal centres of the lymphoid follicles. (4) There are many unanswered questions about the coexistence of the phosphatases and cholinesterases in the same places; their concomitant association in the lymphatic tissue may represent a special case within the framework of a more general mechanism.

Increased proportion of B lymphocytes in human tonsils and appendices

The percentage of T and B lymphocytes was studied in human tonsils and appendices. An increased percentage of B lymphocytes, 59.1% in tonsils and 54.5% in appendices, was found, whilst the percentage of T lymphocytes was 23.6% and 27.9%, respectively. In the peripheral blood of the corresponding figures were 12.5% for B cells and 50% for T cells.

[5-Methoxy-N-acetyltryptamine (melatonin) in enterochromaffin cells]

As evidenced from the action of acetone extracts of the mucous layer of the human appendix, these extracts contain a substance capable of bleaching the frog's skin. Model experiments with 0.1% adrenaline, 0.2% noradrenaline, 2.5% hydrocortisone and solutions of various concentrations of synthesized melatonin permitted to identify the above substance as melatonin. The bleaching aciton dependence on the number of enterochromaffin cells (Ec-cells) in the mucous layer of the appendix, and the presence of serotonin in Ec-cells reveal a connection between melatonin and Ec-cells. An average content of 5-methoxy-N-acetyltryptamine in the human appendix amounts to 0.004 mg per 100 Ec-cells. It is suggested that the epiphysis and enterochromaffin cells compose a common functional neuroendocrine system playing a definite role in maintaining the homeostasis of the organism.

Microspectrophotometric detection of heparin in mast cells and basophilic granulocytes stained metachromatically with Toluidine Blue O

A qualitative microspectrophotometric detection method for heparin in situ has been developed, using data obtained previously with a model system of polyacrylamide films containing pure glycosaminoglycans (Tas, 1975). This technique, based on the unique metachromatic properties of heparin with Toluidine Blue O in glycerol, has been worked out with rat peritoneal and mesenteric mast cells. After the smears containing the stained cells had been mounted in glycerol, a change with time of the recorded metachromatic peaks to lower wavelengths was found, leading to an equilibrium phase after some days. The metachromatic peaks recorded in this phase appeared to resemble closely the peak obtained for the heparin-Toluidine Blue O complex under similar conditions in the model experiments. With rat mast cells it was found that nucleic acids, basic proteins, histamine and lipids had no appreciable influence on the position of the final recorded peaks, nor did they influence the slope of the time course very much. This observed decrease with time in the wavelengths of the metachromatic peaks can be explained by the time necessary for equilibration of the cells in glycerol and by the possible influence of lower sulphated glycosaminoglycans on the peak of the heparin-Toluidine Blue O complex. It was found that the method can be used to detect unequivocally the presence of heparin in cells, even if they also contain up to 75% (mole/mole) of other, lower sulphated glycosaminoglycan. Only a limited number of cells is necessary with this method - in contrast to biochemical determinations. For the first time the presence of heparin in normal human basophilic granulocytes and mast cells has been proved directly. The experiments indicate the occurrence of virtually similar sulphated heparins in human mast cells and basophilic granulocytes, as well as in pig mast cells. A higher sulphated heparin, however, might be present in rat mast cells.

Early lymphoepithelial relationships in human appendix. A combined light- and electron-microscopic study

The fine structure of human appendix was studied from the earliest stages of lymphoid development in fetuses to the definitive relationships found in children up to 8 years old. Follicular accumulations of lymphocytes were observed first in the mesenchyme immediately beneath epithelium which contained a predominance of goblet cells on the surface and in the crypts. Larger accumulations of lymphoid cells in older fetuses were intimately related to surface epithelium but not to the epithelium of crypts. At the point of invasion of lymphoid cells into surface epithelium, the goblet cell population diminished and epithelial cells displaying a morphologically distinct form of differentiation were observed. They were characterized by the presence of irregular microvilli or microfolds and numerous apical micropinocytotic vesciles. This follicle-associated epithelium (FAE) appeared ultrastructurally identical with epithelium in chicken bursa of Fabricius, mouse Peyer's patch, and rabbit appendix, which has been shown to be capable of transporting ferritin and India ink tracer from the lumen to underlying tissue. It appeared identical to specialized epithelial cells of adult human Peyer's patches. FAE was maintained through the neonatal period into childhood. We speculate that the biological significance of FAE is to provide a channel through which antigens may stimulate clonal proliferation and seeding of B-lymphocytes throughout the lamina propria of internal mucous surfaces.

Rabbit Peyer's patches, appendix, and popliteal lymph node B lymphocytes: a comparative analysis of their membrane immunoglobulin components and plasma cell precursor potential

We have characterized and compared the differentiative potential of B lymphocytes obtained from rabbit appendix (APP), Peyer's patches (PP), and popliteal lymph nodes (PLN) by immunofluorescence analysis of membrane immunoglobulin (Ig) components, by radioiodination of membrane components followed by isolation and identification of cell surface Ig, and by cell transfer studies. As assessed by cell transfer lymphoid cells from PP and APP appear to be highly enriched sources of IgA plasma cell precursors. In addition, these populations of lymphocytes have a small but significant potential to give rise to IgM and IgG plasma cells. In contrast, as shown previously (1), lymphocytes from PLN have a comparatively small potential to generate IgA plasma cells. The ability of cells from PLN and PP to give rise to plasma cells is correlated with the presence of 35 to 38% of lymphocytes from both sources having membrane light chain determinants detectable by immunofluorescent staining. When the cells were stained directly for mu chain determinants, about 33% of PLN cells and 28% of PP cells were positive. These latter percentages were shown to reflect cells bearing both endogenously synthesized b4 light chain and mu heavy chain. By indirect immunofluorescence, alpha and gamma chain determinants were also detected on PP and PLN cells; however, these Ig did not appear to be products of the cells which bore them as they were not regenerated after removal of Pronase. It was further demonstrated that purified rabbit copro-sIgA and colostral sIgA are cytophilic for PP and PLN cells. The results are discussed with respect to the origin of IgA plasma cells and the postulated bursal role of mammalian gut-associated lymphoid tissue.