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Results for “Lymphoid Tissue”

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At least 613 records · Page 34Linked to original sources

PubMed1997

Differential expression of apoptosis, Bcl-x and c-Myc in normal and malignant lymphoid tissues.

Bcl-x and c-Myc have an important role for the immune response by regulating the programmed cell death (apoptosis) of lymphocytes. Dysfunction of these selection processes can lead to the development of malignant lymphoma. The present study aimed at defining the differential expression of apoptosis, Bcl-x and c-Myc in normal and in malignant lymphoid tissues. Follicular centre lymphoma (FCL-F) and mantle cell lymphoma (MCL) contained the lowest apoptotic indices (AIs), whereas Burkitt's lymphoma (BL) had the highest AIs. The AIs correlated significantly with the growth rates of the tumours and with the extent of Bcl-x expression. Bcl-x was expressed in almost all BL cells, but in few tumour cells in FCL-F and in MCL. c-Myc, in contrast, was found in the majority of the tumour cells in FCL-F and in MCL, but not in BL. Whereas the extent of Bcl-x expression correlated positively with the growth rates, an inverse correlation was observed between the percentages of c-Myc-positive tumour cells and the growth rates of the tumours. We conclude that normal and malignant lymphoid tissues have a distinct pattern of apoptosis and that expression of Bcl-x and c-Myc in B cell lymphoma is differentially regulated.

Apoptosis↗

PubMed1994

Expression of short and long forms of prolactin receptor in murine lymphoid tissues.

Two different forms of the prolactin receptor, differing in the length of their cytoplasmic domains, have been characterized in many tissues of rodents. To better understand whether short and long forms of PRLR are involved in the immune effects of PRL, we evaluated the distribution of these different forms in the thymus, spleen, lymph nodes and bone marrow from rats and mice. Total RNA was used for cDNA synthesis which was amplified by PCR, using oligonucleotides specific to the different forms of the prolactin receptor. We detected transcripts encoding both forms of prolactin receptor in all lymphoid tissues examined in mouse and rat. Finally we studied the transcript encoding prolactin itself in these rodent tissues; a clear signal was only found in rat thymus. The ubiquitous presence of both forms of receptor transcripts in different lymphoid tissues points to an important role of the PRLR and suggests that such forms of the receptor may be involved in differential functions in lymphocytes.

Animals↗

PubMed2005

Primary hepatic marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue type in a liver transplant patient with hepatitis B cirrhosis.

We describe the clinical, histological, and immunohistochemical features of primary hepatic low grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) in a liver transplant recipient with hepatitis B cirrhosis. MALT lymphomas arise in organs normally devoid of lymphoid tissue, which accumulates as a consequence of chronic antigenic stimulation associated with chronic infection or autoimmune disease. Primary hepatic MALT lymphoma is extremely rare; 13 cases have been reported worldwide to date. Our patient is the first case of primary hepatic MALT lymphoma associated with hepatitis B cirrhosis who was treated with orthotopic liver transplantation.

Hepatitis B↗

PubMed2001

Productive infection of T cells in lymphoid tissues during primary and early human immunodeficiency virus infection.

Current models suggest that during human immunodeficiency virus type 1 (HIV-1) transmission virions are selected that use the CCR5 chemokine receptor on macrophages and/or dendritic cells. A gradual evolution to CXCR4 chemokine receptor use causes a shift in the proportion of productively infected cells to the CD4 cell population. Productively infected cells during acute and early infection in lymphoid tissue were assessed, as well as the impact of productive infection on the T cell population in 21 persons who had biopsies performed on days 2-280 after symptoms of acute HIV-1 seroconversion. Even in the earliest stages of infection, most productively infected cells were T lymphocytes. There were sufficient infected cells in lymphoid tissue (LT) to account for virus production and virus load in plasma. Despite the relatively high frequency of productively infected cells in LT, the impact on the size of the T cell population in LT at this stage was minor.

CD4-Positive T-Lymphocytes↗

PubMed1991

Expression of the HOX-2.3 homeobox gene in human lymphocytes and lymphoid tissues.

Homeobox proteins are sequence-specific DNA-binding proteins initially implicated in the control of gene expression in developing tissues; however, there is increasing evidence that these proteins are important in gene regulation in adult tissues. A cDNA for the homeobox gene HOX-2.3 was isolated from an adult human B-lymphocyte cDNA library. Northern blot analysis showed expression of a 1.1 and a 1.6 kb messenger RNA (mRNA) in a human B-cell line. RNase protection assays demonstrated variable expression in both human B- and T-cell lines. Virally transformed and nontransformed lymphocyte cell lines expressed HOX-2.3 transcripts. Essentially no transcripts were found in unactivated normal B and T lymphocytes; however, B-cell activation with Staphylococcus aureus Cowan strain I and phorbol myristate acetate (PMA) or T-cell activation with phytohemagglutinin and PMA were accompanied by a rapid induction of HOX-2.3 expression even in the presence of the protein synthesis inhibitor, cycloheximide. In situ hybridization was performed to examine HOX-2.3 expression in lymphoid tissues. HOX-2.3 mRNA was detected in the thymic cortex from an 8-year-old child, in the germinal centers in adult tonsil, and in a limited number of hematopoietic cells from the bone marrow. These findings suggest the involvement of HOX-2.3 in regulating gene transcription not only in developing tissues but in hematopoietic and lymphoid tissues as well.

Adult↗

PubMed1988

Ontogenic development of gut-associated lymphoid tissue in the rat. An immunohistochemical study.

The development of gut-associated lymphoid tissue (GALT) in the rat was investigated, with special reference to the behavior and ultrastructure of Ia(+) cells during the development of Peyer's patches (PP). At birth, Ia(+) cells were randomly scattered in the lamina propria. From three days, small aggregates of CD4(+), Ia(+), CD5(-) and IL-1(+) cells were observed in the lamina propria. Immunoelectron microscopically, these appeared as mixed populations of dendritic cells, capillary endothelial cells, fibroblast-like spindle cells and lymphocytes. In addition, CD8(+), CD4(-) and IL-1(-) cells were present in the interepithelial space. By seven days, lymphoid follicles were recognizable in the lamina propria, each with an aggregate of IgM-positive small lymphocytes at its center, surrounded by CD4(+) or CD8(+) lymphocytes. Between the 10th and 14th days, these follicles were covered with single-layered, specially differentiated epithelial cells, and structures resembling PP were formed. IgA plasma cells were identified in the lamina propria between the third and the fourth weeks. We speculate that the PP developed from aggregates of Ia(+), IL-1(+) spindle- or dendritic-shaped cells in the lamina propria. The PP were structurally complete by two weeks, although establishment of the characteristic distribution of GALT components evident in the adult took more than six weeks.

Animals↗

PubMed1983

Malignant lymphoma of mucosa-associated lymphoid tissue. A distinctive type of B-cell lymphoma.

As illustrated in the two cases described in this paper close morphologic and immunohistochemical similarities exist between Mediterranean lymphoma (MTL) and primary gastrointestinal lymphoma of follicle center cell (FCC) origin as it occurs in Western countries. Similarities between the two conditions include a dense noninvasive monotypic lamina propria plasma cell infiltrate, present in all cases of MTL and in some cases of Western gastrointestinal FCC lymphoma, and an invasive infiltrate of FCCs morphologically distinct from the plasma cells. A distinctive lesion produced by individual gland invasion characterizes both types of lymphoma. A clonal relationship between the lamina propria plasma cells and the invasive FCCs, long suspected but never proved in MTL, can be demonstrated in Western cases. Many of the histologic and clinical features common to these lymphomas can be explained in the context of the normal maturation sequences of gut associated lymphoid tissue. It is suggested that MTL and Western cases of primary FCC gastrointestinal lymphoma share a common histogenesis from mucosa associated lymphoid tissue.

Adult↗

PubMed1991

An immunohistochemical study on the effects of cyclosporin on the gut-associated lymphoid tissue of rats.

The effect of Cyclosporin (CS) on the gut-associated lymphoid tissue (GALT) of inbred WKA rats was immunohistochemically studied by the immunoperoxidase method. CS in olive oil was orally administered daily for seven days at the dose of 25, 50 and 100 mg/kg/day. On days 1, 4 and 7 of CS administration, rats were sacrificed under ether anesthesia. By CS administration, the decrease and disappearance of Ia antigen expression were dose-dependently recognized on the epithelial cells and the overlaying cells of Peyer's patches. The reduced cellular population and Ia expression of lymphocytes of the follicle and the disappearance of the germinal center also occurred, and Ia-positive dendritic non-lymphoid cells in Peyer's patches and endothelial cells of capillaries in the lamina propria disappeared on day 7 of CS administration. In addition, a temporary increase of W3/25-positive cells and the appearance of Ia-positive intra-epithelial cells were observed on day 4. Simultaneously, interleukin 2 receptor (IL-2R)-positive cells gradually decreased on day 4, and almost disappeared on day 7. From these results, it is speculated that CS suppresses not only interleukin 2 (IL-2) production as previously reported, but also the expression of Ia antigens and IL-2R. It may well suppress the immune system at the point of recognition and presentation of alloantigen, and the proliferation and differentiation of B cells.

Animals↗

PubMedDate not supplied

Combined liver-spleen-small intestine grafting in a rat model: role of transplanting additional lymphoid tissue on survival.

The aim of this study was to develop suitable models of combined intestinal grafting to examine the enhancing effect of intestinal grafting with additional lymphoid tissue using 30% of the liver mass and the whole spleen on recipient survival in the absence of immunosuppression. Grafts from DA (RT1a) rats were transplanted orthotopically to PVG (RT1(1)) recipients according to the following design: group 1 (n = 6), en bloc 30% liver/entire SB/spleen; group 2 (n = 7), en bloc 30% liver/SB; group 3 (n = 7), SB/spleen and group 4 (n = 7), SB control for the preceding groups. The orthotopic nature and proximal interposition of the SB graft allowed the assessment of protection afforded by components of the cluster on the SB graft using survival endpoints. Although group 4 hosts survived half as long compared to other groups, statistical significance was reached only in the case of group 1; group 1 MST equalled 15.3 days, significantly higher than group 4 (p = 0.01). Acute rejection was present in every grafted tissue and was equivalent whether liver was included or excluded in the cluster. GVHD was absent postoperatively using clinical or histological criteria; recipient spleens showed hyperplasia, donor spleens depicted lymphocytic depletion on histology. This study determined that statistically proven enhanced survival was obtained only after grafting 30% liver plus spleen with the entire SB. GVHD was rare in the fully allogeneic system despite transplanting a massive load of lymphoid tissue. The surgical models used in this study employing liver in the cluster, address the important question of how best to evaluate the role of heterotopic accessory liver grafting in providing tolerance to co-transplanted small intestine.

Animals↗

PubMed2002

Presence of host ICAM-1 in laboratory and clinical strains of human immunodeficiency virus type 1 increases virus infectivity and CD4(+)-T-cell depletion in human lymphoid tissue, a major site of replication in vivo.

Human immunodeficiency virus type 1 (HIV-1) incorporates several host proteins. Earlier studies have indicated that such foreign constituents can modulate the virus life cycle, although the potential roles that these proteins might play in the viral pathology in vivo remain unclear. In an attempt to shed light on this issue, we first exposed explants of human lymphoid tissue to isogenic viruses except for the presence or absence of host-derived ICAM-1. Incorporation of ICAM-1 alone increased HIV-1 infectivity for human tonsillar tissue cultured ex vivo. This observation was made for viruses bearing distinct coreceptor utilization profiles. Conversion of LFA-1 to a high-affinity-high-avidity state for ICAM-1 further augmented the susceptibility of human tonsillar histocultures to infection by ICAM-1-bearing virions. A more massive depletion of CD4(+) T lymphocytes was seen with X4 ICAM-1/POS viruses than with isogenic ICAM-1/NEG virions. Exposure of X4 and R5 primary isolates of HIV-1 to a blocking anti-ICAM-1 antibody resulted in a decrease of virus infection. Finally, X4 and R5 virions derived from a natural human lymphoid tissue microenvironment incorporated high levels of ICAM-1. Altogether, these results indicate that the incorporation of host ICAM-1 can significantly modulate the biology of HIV-1 in a cellular milieu recognized as the major site of replication in vivo and suggest that host proteins found in HIV-1 particles may participate in the pathogenesis of this disease.

CD4-Positive T-Lymphocytes↗

PubMed1998

HIV type 1 infection in lymphoid tissue: natural history and model systems.

The pathogenesis of human immunodeficiency virus (HIV) in the lymphoid compartment has a dramatic effect on disease progression and important implications for therapeutic and vaccine strategies. Here we discuss current understanding of the pathogenesis of HIV in the lymphoid tissue. Various model systems that allow examination of the effect of retroviral infection in primary lymphoid organs are discussed, as well as current progress made with the use of these systems, with particular emphasis on the SCID-hu mouse.

Animals↗

PubMed2006

Effect of R77Q, R77A and R80A changes in Vpr on HIV-1 replication and CD4 T cell depletion in human lymphoid tissue ex vivo.

BACKGROUND: It has been suggested that mutations of R77A and R80A in the HIV-1 viral protein R (Vpr) impair its proapoptotic activity and that a naturally occurring R77Q variation is associated with non-progressive HIV-1 infection. RATIONALE: To assess the effect of Vpr R77Q, R77A and R80A mutations on the efficiency of CCR5(R5)- and CXCR4(X4)-tropic HIV-1 replication and cytopathicity in human lymphoid tissue (HLT). METHODS: Vpr mutants of the X4-tropic HIV-1 NL4-3 clone and an R5-tropic derivative were generated by PCR mutagenesis. Virus stocks established by transfection of 293T cells were used to infect macrophages and ex vivo HLT. HIV-1 replication was assessed by measuring p24 core antigen in the culture supernatants and CD4 T-cell depletion and apoptosis were measured by flow cytometric analysis. RESULTS: The R5-tropic HIV-1 Vpr mutants replicated with slightly (R77A, R77Q) to moderately (R80A) reduced efficiency in ex vivo-infected HLT and macrophages. In comparison, the changes in Vpr had negligible effects on replication of the X4-tropic forms in lymphatic tissues. Mutation of R77Q and R80A reduced apoptosis of HIV-1-infected cells in ex vivo-infected HLT independently of the viral coreceptor tropism. However, only the R5-tropic HIV-1 Vpr mutants caused markedly less CD4 T-cell depletion than wild-type HIV-1 at the end of ex vivo HLT culture. CONCLUSIONS: The observation that Vpr R77Q reduces the cytopathicity of R5-tropic HIV-1 in lymphoid tissues supports a role in non-progressive HIV-1 infection but the attenuating effects might be dependent on the viral subtype and coreceptor tropism.

Apoptosis↗

PubMedDate not supplied

[Methylation of DNA from rat lymphoid tissues in development of immune response].

Within 4 days after immunization of rats by means of sheep erythrocyte suspension (of various concentration) analysis of nucleotide composition of DNA, isolated from the animal lymphoid tissue, was carried out using cellulose thin-layer chromatography. The immunization was shown to affect distinctly the DNA methylation in rat lymphoid tissue; sometimes, it altered the DNA nucleotide composition. The data obtained correspond with the well-recognized phenomenon on dependence of the immune response on the antigen concentration.

Animals↗

PubMed1996

Mucosa-associated lymphoid tissue in middle ear and Eustachian tube in children.

The presence of mucosal lymphoid follicles with germinal centers, so called mucosa-associated lymphoid tissue (MALT), in the Eustachian tube (ET) and middle ear (ME) was investigated in 23 human temporal bones containing the entire ET obtained from 23 children, 3 months to 10 years old at death. Greater numbers of MALTs were found in specimens from children with otitis media (OM) than from those without OM. MALT showed a wedge-shaped distribution through the ME and ET: in all 3 specimens that had MALTs in the ME, these tissues were seen throughout the ET; in all 4 specimens with MALTs in the bony portion of the ET, these tissues were present both in the tympanic and pharyngeal portions of the cartilagines ET; all 7 specimens that had MALTs in the tympanic half of the cartilagines ET had MALTs in the pharyngeal portion of the cartilagines ET as well. Furthermore, MALTs were noted in the pharyngeal portion of the ET in more than half of the specimens without OM but in none of the MEs of specimens without OM. These results support the hypothesis that persistent and recurrent inflammation in the nasopharynx spreads through the ET to play a role in the pathogenesis of chronic OM in children.

Cartilage↗

PubMed1985

Histological changes in rat bronchus-associated lymphoid tissue after administration of five different antigens.

Histological changes in bronchus-associated lymphoid tissue (BALT) following single intratracheal administration of five different antigens were studied in the rat. After administration of T-dependent antigens (i.e., horseradish peroxidase, bovine serum albumin, and Bacillus Calmette Guérin) only minor changes in BALT in the rat occurred. Intratracheal administration of a T-independent antigen (lipopolysaccharide) and a partly T-independent antigen (paratyphoid vaccine) resulted after 1 week in an increase in cytoplasmic IgM-containing (cIgM) blast cells and plasma cells; these appeared to enter via the high endothelial venules (HEV). After 6 weeks, germinal centers were seen.

Animals↗

PubMed1992

Low incidence of bronchus-associated lymphoid tissue (BALT) in chronically inflamed human lungs.

The relevance of bronchus-associated lymphoid tissue (BALT) in man is still under discussion. Animal experiments indicate that the development of BALT is dependent on microbial stimulation. Therefore, the incidence of BALT was investigated retrospectively in specimens removed during surgical procedures on patients with chronic pulmonary inflammation. All these patients had severe chronic bronchitis and bronchiectasis, but BALT was found in only 8%. In patients with BALT and a malignant tumor, occlusion of a bronchus with poststenotic pneumonia was always present and BALT was observed exclusively in areas peripheral to the occlusion. In man other compartments of the lung must be responsible for the immune function of BALT found in animals.

Adolescent↗

PubMed1992

Cytogenetic study of B-cell lymphoma of mucosa-associated lymphoid tissue.

The recently described B-cell lymphomas arising in mucosa-associated lymphoid tissue (MALT) form a distinct clinico-pathologic group of non-Hodgkin's lymphoma, and therefore would be expected to be characterized by a recurrent chromosomal aberration. We have analyzed the cytogenetics of 23 cases of MALT lymphomas arising in the stomach, small intestine, lung, and lacrimal gland. In each case the presence of an abnormal clonal cell population was confirmed by the identification of rearranged bands when digested tumor DNA was hybridized with a probe to the joining region of the immunoglobulin heavy chain gene. Metaphase spreads were obtained in 14 cases, of which 9 cases showed an abnormal karyotype. Although no unifying aberration was detected, rearrangements of chromosome 1p, and numerical abnormalities of chromosomes 3 and 7, may play a role in the genesis of these tumors.

Chromosome Aberrations↗

PubMed1986

Dome epithelial M cells dissociated from rabbit gut-associated lymphoid tissues.

Dome and dome epithelial cells were selectively dissociated from gut-associated lymphoid tissues of rabbits. Sequential tissue washes in dithiothreitol, EDTA, and collagenase removed the dome epithelium, without disrupting the follicles or villi, and provided a cell suspension containing 74 +/- 6% lymphocytes, 9 +/- 4% columnar epithelial cells, 10 +/- 7% tangible-body macrophages, and 4 +/- 2% M cells (follicle-associated epithelial cells). The last mentioned cells were characterized by transmission electron microscopy as large (20 to 55 microns diameter) cuboidal, round, or oval cells with eccentric nuclei and thin membranous processes surrounding empty vacuoles. The M cells were occasionally joined together by tight junctions. Histochemical and immunocytochemical analyses of M cells with the light microscope showed that they were devoid of immunoglobulins and negative for T-cell antigen and secretory component and had no detectable alkaline phosphatase or endogenous peroxidase activity. The M cells had few vacuoles with faint acid phosphatase activity; nonspecific neutral esterase was abundant. Possible uses for dome and dome epithelial cells are discussed.

Acid Phosphatase↗