B Cells in the appendix and other lymphoid organs of the rabbit: stimulation of DNA synthesis by anti-immunoglobulin

A morphological and immunohistological study of the human and rabbit appendix for comparison with the avian bursa

Diversification of the primary antibody repertoire occurs in young rabbit appendix. As a prelude to molecular investigation of whether human appendix has a similar role, we compared the lymphoid morphology and distribution of common B- and T-cell subsets in frozen and/or paraffin-embedded normal appendix specimens at various ages. IgA, IgM and IgG staining patterns were similar in frozen human and rabbit appendices. The elongated follicles of the young human and rabbit appendices regressed with age to resemble Peyer's patches. Although similar in morphology to the bursa, human and rabbit appendix follicles differ in that they do not involute completely with age and contain significant numbers of germinal center (GC) T cells although the number is low early in life. If the human appendix functions as a primary lymphoid organ, it may occur during the first few months of age when the GC T-cell density is low.

Neonatal appendectomy impairs mucosal immunity in rabbits

We compared the effects of neonatal appendectomy in rabbits on total Ig and antigen (Ag)-specific Ig levels in the serum and gut, and on plasma cell numbers in the small intestine in response to intraperitoneal (i.p.) and intraduodenal (i.d.) immunizations with ovalbumin (OVA). Animals were sacrificed after 9 weeks. Antibodies (Abs) in the duodenum were collected and quantified by enzyme-linked immunosorbent assay (ELISA) while plasma cells were quantified by double immunofluorescent staining. Appendectomy markedly reduced total intestinal IgA (P < 0.0006), IgM (P < 0.003), and IgG (P < 0.05) relative to controls, whereas total serum Ig levels were not lowered significantly. Moreover, appendectomy nearly ablated OVA-specific IgA (P < 0.007) in the gut and severely depleted OVA-specific IgG in the gut (P < 0.03) and serum (P < 0.007). The sharp decreases in total IgA and anti-OVA IgA were paralleled by decreases in total IgA+ plasma cells (P < 0.0005) and OVA-reactive IgA+ plasma cells (P < 0.05). These results support a major role of the rabbit appendix in seeding the intestinal lamina propria with plasma cell precursors, especially those producing IgA.

T-cell lymphomas of the stomach: morphological and immunological studies characterizing two cases of T-cell lymphoma

Using cytochemical, electron microscopic and immunohistochemical techniques in 20 primary malignant lymphomas of the stomach, we found 18 B-cell and 2 T-cell lymphomas. Primary T-cell lymphoma in the stomach has not been previously reported. The T cells in both cases were reminiscent of T immunoblasts with prominent nucleoli and a basophilic cytoplasm. Case 1 showed a cytological relationship to pleomorphic T-cell lymphoma, large cell type. Case 2 contained in addition some cells not previously described in T-cell lymphomas, resembling immature plasma cells with abundant rough endoplasmic reticulum. Focal positivity to acid phosphatase and dipeptidylaminopeptidase IV suggests the T-cell nature of both lymphomas. In both cases the tumour cells were OKT 11 and OKT 4 positive, and negative for OKT 8. Thus, both cases represent high-grade malignant T-cell lymphomas which correspond phenotypically to T-helper cell lymphoma. Case 2 revealed a further immunohistochemical peculiarity: atypical immunoblasts reacted positively with Ki-1 antibody. Thus, it is a Ki-1 lymphoma of T-cell type.

Novel differences in the characteristics of spleen and peripheral blood lymphocytes activated by anti-immunoglobulin

A comparison of splenocytes and peripheral blood lymphocytes with regard to activation by anti-immunoglobulin revealed distinctions in the behavior of the populations. Thus, a three- to fourfold greater concentration of anti-immunoglobulin was required to achieve one-half maximal activation of splenocytes than that required for peripheral blood lymphocytes. This difference cannot be accounted for on the basis of binding data. That is, although the binding of 125I-labeled anti-immunoglobulin was found to be slightly greater for peripheral blood lymphocytes than for spleen cells, the concentration required for one-half maximal binding was essentially the same for the two populations. Other differences between the populations were also observed. For example, splenocytes but not peripheral blood lymphocytes were substantially inhibited in terms of activation by anti-immunoglobulin subsequent to the absorption and elution of cells from anti-immunoglobulin-coated petri plates at 4 degrees C, despite the fact that the recovery of cells in general and B cells in particular following absorption and elution from anti-immunoglobulin coated plates at 4 degrees C was essentially the same for both populations.

Appendectomy and subsequent cancer risk

Although earlier epidemiologic studies reported a positive association between appendectomy and certain cancers, interest was limited due to lack of confidence in the study findings. However, recent morphologic studies on the immune structure of the vermiform appendix in the rabbit and man argue for a reevaluation of the appendectomy--cancer association. This paper reviews briefly the morphologic and epidemiologic literature on the subject to date. The validity of the earlier epidemiologic findings is discussed and avenues for further research assessing the relationship of appendectomy to subsequent cancer risk are proposed.

Origin and fate of IgE-bearing lymphocytes. I. Peyer's patches as differentiation site of cells. Simultaneously bearing IgA and IgE

Peyer's patches (PP) from adult conventionally raised (C) and germ-free (GF) rats of the same age differed strikingly in the distributions of cells bearing membrane-bound immunoglobulin of the different isotypes. High concentrations of cells with membrane-bound IgE (approximately 20% of total cells determined by indirect immunofluorescence) were found in PP of rats, whereas IgE+ cells were absent from PP of C rats. The numbers of IgA+ cells were almost threefold higher in PP of GF rats when compared with C rats. In contrast, PP of GF rats had greatly reduced numbers of IgM-bearing cells (4%) when compared with C rats (23%); in some experiments virtually no IgM-bearing cells were detected. The levels of IgA- and IgE-bearing cells in spleen of GF rats were increased (to 11% and 7%, respectively). Of the IgE-bearing cells in PP and spleen of GF rats, approximately one-half were simultaneously positive for IgA. When these PP cells were treated with pronase to remove membrane bound immunoglobulins and maintained in culture, both IgE and IgA reappeared within 12 h. The proportion of doubly labeled cells was similar to that of the untreated population. No IgE+ cells were detected in bone marrow of C of GF rats at any time, in agreement with the findings of Ishizaka et al., although up to 20% of bone marrow cells bore other immunoglobulin isotypes, suggesting that IgE-bearing cells arise in the PP either de novo or by switching from precursors carrying IgM or IgA.

Qualitative and quantitative morphologic study of Peyer's patches of the mouse after neonatal thymectomy and hydrocortisone injection

Peyer's patches in normal adult mice, neonatally thymectomized mice and mice injected with hydrocortisone were studied qualitatively and quantitatively by light microscopy. The patch was divided into germinal center, follicular area, parafollicular area and dome area. In normal mice, the volumetric ratio of the germinal center to the entire patch was 30.9%; that of the follicular area, 33.3%; that of the parafollicular area, 27.7%; and that of the dome area, 8.2%. Thymus-dependent small lymphocytes were 40% of small lymphocytes in the patch. Out of the total thymus-dependent small lymphocytes in the patch, 13% were included in the germinal center; 19%, in the follicular area; 62%, in the parafollicular area; and 6%, in the dome area. Hydrocortisone-sensitive small lymphocytes were 65% of the total small lymphocytes in the patch, the germinal center contained 9%; the follicular area, 84%; the parafollicular area, 2%; and the dome area, 5%. The epithelium over the dome area was invaded by numerous small lymphocytes. Forty-eight percent of lymphocytes within the epithelium over the dome were thymus-dependent and 67% were hydrocortisone-sensitive. It is concluded that Peyer's patch may be considered as a peripheral lymphatic tissue, functionally as well as morphologically.