Lack of influence of Peyer's patches on the intestinal localization of mesenteric lymphoblasts

Immunology of gastrointestinal lymphoma

Experimental work showing that IgA plasma cell precursors activated in gut associated lymphoid tissue (GALT) of rats and sheep migrate to the lamina propria of the gut via the regional lymphatics, mesenteric lymph node and blood, has been supported by immunohistochemical studies. In rats, immunoblasts with cytoplasmic IgA are present in the Peyer's patches in association with the high endothelial venules which is probably an important, though not the only, site of extravasation into the gut, whereas cells with cytoplasmic IgA are rarely observed in the dome regions of Peyer's patches. Immunohistochemical studies of human Peyer's patches have revealed differences between the distribution of cells with cytoplasmic IgA in man compared to rats. In man, immunoblasts with cytoplasmic IgA are not concentrated in the zone of cells containing the high endothelial venules, whereas they are present in the dome regions of the Peyer's patches. The following questions arise: Do precursors of IgA plasma cells activated in human GALT migrate to the lamina propria via the blood, but extravasate predominantly via the capillary network, rather than the high endothelial venules? or do IgA plasma cell precursors 'mature' in situ in the Peyer's patches of man and subsequently migrate laterally to seed the lamina propria? Three lines of evidence from studies of primary B cell lymphomas of GALT support the latter hypothesis: 1) Primary B cell lymphomas of the gut remain localized to GALT for long periods of time; 2) Histological studies of the lymphoid tissue in these lymphomas have shown a gradation of cell types, from the muscularis mucosae towards the mucosal epithelium, which strongly suggests that plasma cells develop in situ in the gut from the adjacent layers of cells; 3) Preliminary studies of DNA extracted from the blood-borne cells from patients with GALT-derived B cell lymphoma have failed to demonstrate the presence of clonal gene rearrangements. Normal and malignant human GALT contains a perifollicular population of B cells with centrocyte-like morphology which lack surface IgD. No direct equivalent can be detected in rodent Peyer's patches. Their quiescent nature and distribution in malignant GALT suggests that they are follicle centre cell-derived and precursors of immunoblasts and plasma cells. As such they may be memory B cells. Their association with epithelium is a consistent feature of normal and malignant GALT which is of unknown but undoubted significance. The function of intraepithelial T cells is still unknown. Malignant T cells in MHI may be derived from intraepithelial T cells.(ABSTRACT TRUNCATED AT 400 WORDS)

A comparative study of the gut-associated lymphoid tissue of primates and rodents

Previous studies have suggested that the gut-associated lymphoid tissue (GALT) of man is distinct from that of laboratory animals, but it is not clear whether this is due to environmental or true species difference. We have made a comparative study of rats and baboons because, like rats, baboons are herbivorous and relatively unhygienic but they are phylogenetically much more closely related to man. The Peyer's patches of rats, baboons and man are morphologically very similar in all three species but phenotypically those of man and baboons are different to those of rats. Cells with irregular nuclei ("centrocyte-like" cells) surround the mantle zone in all three species. While these cells express surface IgD and IgM in rats, in man and baboons they express surface IgM or IgA. A population of immunoblasts which express cytoplasmic IgA are present in association with the high endothelial venules of rat Peyer's patches. These cells are not present to the same extent in man or baboons. This suggests that the events between the antigenic stimulation of Peyer's patches and the ultimate seeding of the lamina propria with IgA secreting plasma cells may be different in rodents and primates.

Mesenteric lymphoblast localization throughout the murine small intestine: temporal analysis relating intestinal length and lymphoblast division

Mesenteric lymphoblasts (MLN) have a predilection to selectively localize in the lamina propria and epithelium of the small intestine. Using an adoptive transfer method, we examined the localization kinetics of these blasts in the intestinal wall with respect to their distribution from duodenum to terminal ileum and also assessed their mitotic activity by autoradiographic techniques. 3H-thymidine-labelled MLN cells were found throughout the small intestine by 6 hr post-transfer and reached a maximum frequency in this organ by 24 hr post-transfer. Donor blasts were most frequent in the duodenum and terminal ileum regions of the gut. Subsequently, the frequency of labelled cells throughout the intestinal wall declined to near zero. The apparent accumulation of MLN blasts in the gut was not related to either a temporary retention and departure from the pulmonary vasculature or to mitotic division of labelled cells in the gut wall. A model describing the relationship between MLN blast localization kinetics in various segments of the intestine was formulated.

Lymphoid stroma of Warthin's tumor: phenotypic analogies with gut-associated lymphoid tissue

Lymphocytes in cell suspensions and cryostat sections of Warthin's tumors (WT) have been phenotypically characterized using a battery of monoclonal and polyclonal antisera to lymphoid cell-associated antigens. The present study shows that in the WT lymphoid stroma, B cells are more numerous than T lymphocytes and include a significant percentage of surface immunoglobulin A-bearing cells. Of the T cells, the Leu 3a+ and OKT4+ lymphocytes are present in higher percentages than the OKT8+ ones. Both T-cell subsets present a topographic distribution which is similar to that found in human tonsils and gut tunica propria. Intraepithelial lymphocytes displaying an OKT8+, Leu 3a-, OKT3- phenotype are also present. These data, together with previous findings which have demonstrated that Warthin's tumor epithelium synthesizes IgA secretory piece, suggest that these cells may modulate the organization of the surrounding lymphoid stroma toward that of a mature lymphatic tissue phenotipically resembling gut-associated lymphoid tissue.

Gut- and bronchus-associated lymphoid tissue

Bronchus-associated and gut-associated lymphoid tissues (BALT and GALT) have both functional and morphologic similarities and are involved in seeding lung, gut, and other mucosal sites with predominantly IgA-containing B cells. Both types of lymphoid tissue are engaged in the regulation and the controlled amplification of immune responses, which vary from positive mucosal responses in both mucosae and peripheral tissues to local mucosal responses and systemic tolerance. Their further involvement in provision of cells destined to reside in the epithelial compartment of the body appears likely but requires further investigation. Their role in the provision of precursors of mucosal mast cells must also be explored further, but some participation in this event appears likely. The mucosa-associated lymphoid tissue (MALT) system appears to be integrated with the systemic immune system but may be considered as separate from it in several functional ways.

An immunohistochemical study of cells with surface and cytoplasmic immunoglobulins in situ in Peyer's patches and lamina propria of rat small intestine

The distribution of cells with surface and cytoplasmic immunoglobulins was studied in Peyer's patches (PP) and intestine of rats, using both frozen and paraffin sections, with a two-step peroxidase technique. Anti IgM, IgG, IgA and IgE sera were used. Surface staining was found within PP with all antisera used. Although the villi contained predominantly IgA plasma cells (PC), IgG PC and a few IgM and IgE PC were also found. Within PP, however, no IgA PC were found but IgM and IgG PC were present in all stages of development, mainly in the dome. PC of all types, but mostly IgA cells, were present in and around high endothelial venules (HEV). The results suggest that IgM and IgG PC precursors can develop to PC within PP whereas IgA precursors do not. PC appear to home to the gut preferentially via HEV.