Biochemical, ultrastructural and molecular characterization of the triphenyltin acetate (TPTA)-induced apoptosis in primary cultures of mouse thymocytes

Triphenyltin acetate (TPTA), a triorganotin compound used in agriculture as a biocide, is immunotoxic in vivo and in vitro. The present study was undertaken to ascertain whether apoptosis might play a role in the TPTA toxicity in vitro. Mouse thymocyte primary cultures were exposed to 0, 4 and 8 micromol/L TPTA; methyl prednisolone (1 micromol/L) was used as a positive control. Cell aliquots were harvested after 0, 1, 2, 4, and 8 h and the presence of early or late apoptotic phenomena was checked by (a) morphological investigations; (b) spectrophotometric quantification of fragmented DNA and agarose gel electrophoresis; (c) cell flow cytofluorometry, using an annexin V-FITC kit; and (d) detection of in situ apoptosis by a colorimetric detection kit (Titer-Tacs). TPTA cytotoxicity was also evaluated using the trypan blue dye exclusion test. Morphological investigation indicated apoptosis and/or necrosis. After 8 h of incubation, cells exposed to 4 micromol/L TPTA showed an increase in DNA fragmentation (on electrophoresis), which was confirmed by spectrophotometry (p < 0.05). Flow cytofluorometry pointed out an early (p < 0.05) increase of annexin V-positive (apoptotic) cells in TPTA-exposed flasks, whereas at least partly contradictory, results were obtained with the Titer-Tacs kit. Overall, these results provide evidence that TPTA, at low concentrations (4 micromol/L) induces early and late apoptotic phenomena, whereas cells exposed to the highest concentrations (8 micromol/L) are likely to undergo necrosis rather than apoptosis.

Blood lymphocyte subsets in canine idiopathic pericardial effusion

The immunophenotype of peripheral blood lymphocytes was investigated in 23 dogs diagnosed with idiopathic pericardial effusion in order to provide information about a possible role of the immune system in this pathology. Flow cytometric analysis showed a significant reduction in nearly all lymphocyte subsets examined and a strong, significant (P < 0.001) reduction of the CD4 subset, which gave rise to a significantly lower CD4/CD8 ratio. Our data suggest that an imbalance in the immune system is present during the course of the disease, preferentially affecting the T helper cell response.

Cytokine gene expression in neoplastic B cells from human mantle cell, follicular, and marginal zone lymphomas and in their postulated normal counterparts

Cytokines may promote tumor growth by paracrine and/or autocrine pathways. Little information is available because malignant cells differ from their normal counterparts for the cytokine repertoire they express. Here we have investigated by reverse transcription-PCR the expression of 22 cytokine genes in neoplastic B lymphocytes from six patients with mantle cell lymphoma, 10 with follicular lymphoma, and 5 with marginal zone lymphoma and in their normal counterparts, i.e., naive, germinal center, and memory B cells, purified from tonsils. The overall profiles of cytokine gene expression in neoplastic B cells and in the corresponding normal B-cell subsets were similar, but some "holes" in the repertoire of malignant versus normal B lymphocytes were detected. Different "hole" combinations were identified consistently in mantle cell lymphoma, follicular lymphoma, and marginal zone lymphoma, thus representing molecular fingerprints of each individual lymphoma entity.

Expression and function of IL-12 and IL-18 receptors on human tonsillar B cells

IL-12 activates murine and human B cells, but little information is available as to the expression and function of IL-12R on human B lymphocytes. Here we show that the latter cells, freshly isolated from human tonsils, expressed the transcripts of both beta1 and beta2 chains of IL-12R and that beta2 chain mRNA was selectively increased (4- to 5-fold) by incubation with Staphylococcus aureus Cowan I bacteria or IL-12. B cell stimulation with IL-12 induced de novo expression of the transcripts of the two chains of IL-18R, i.e., IL-1 receptor-related protein and accessory protein-like. Functional studies showed that both IL-12 and IL-18 signaled to B cells through the NF-kappaB pathway. In the case of IL-12, no involvement of STAT transcription factors, and in particular of STAT-4, was detected. c-rel and p50 were identified as the members of NF-kappaB family involved in IL-12-mediated signal transduction to B cells. IL-12 and IL-18 synergized in the induction of IFN-gamma production by tonsillar B cells, but not in the stimulation of B cell differentiation, although either cytokine promoted IgM secretion in culture supernatants. Finally, naive but not germinal center or memory, tonsillar B cells were identified as the exclusive IL-12 targets in terms of induction of NF-kappaB activation and of IFN-gamma production.

Stromal cell-derived factor-1 as a chemoattractant for follicular center lymphoma B cells

BACKGROUND

Follicular center lymphoma displays widespread lymph node involvement at diagnosis. The chemoattractants that control the locomotion of follicular center lymphoma B cells have not been established. Stromal cell-derived factor-1 (SDF-1) is a CXC-class chemokine that enhances the migration of normal human B cells and is expressed in peripheral lymphoid tissues. Here we have investigated 1) whether SDF-1 stimulates the in vitro locomotion of follicular center lymphoma B cells and of their presumed normal counterparts (i. e., germinal center B cells) and 2) whether the same cells express SDF-1 transcripts.

METHODS

B cells were purified by immunomagnetic bead manipulation. Messenger RNA was detected by reverse transcription-polymerase chain reaction. Migration was assessed by the filter and collagen invasion assays. All P values were two sided.

RESULTS

Follicular center lymphoma B lymphocytes showed a statistically significant migratory response to 300 ng/mL SDF-1, both in the filter and in the collagen assays (P =.002 for each). Such response was mediated by the SDF-1 receptor, CXCR4. CD40 monoclonal antibody (MAb) and tonsillar germinal center B cells treated with CD40 MAb and recombinant interleukin 4, but not freshly isolated, migrated statistically significantly faster in the presence than in the absence of SDF-1 (P =.002 in both filter and collagen assays). Freshly isolated follicular center lymphoma and germinal center B cells expressed SDF-1 transcripts.

CONCLUSIONS

This study shows that SDF-1 substantially enhances the migration of follicular center lymphoma B cells but not the migration of freshly purified germinal center B cells. This difference may be related to the extended survival of follicular center lymphoma versus germinal center B cells. SDF-1 produced in follicular center lymphoma lymph nodes may play a role in the local dissemination of tumor cells.

Effects of subclinical bovine paratuberculosis on in-vitro polymorphonuclear neutrophil migration

Migration of polymorphonuclear neutrophils (PMNs) [unstimulated or stimulated with zymosan-activated serum (ZAS)] from 18 cows was measured in a microwell filter assay. Of these animals, 10 were subclinically infected with Mycobacterium paratuberculosis and shown by culture to be excreting the organism in the faeces; the remaining eight were clinically normal and negative for M. paratuberculosis on faecal culture. PMN "net migration" (stimulated minus unstimulated cells) of the infected cows was significantly lower than that of the uninfected cows. Migration of unstimulated cells in the infected cows did not differ from that in the uninfected cows. It would therefore appear that the infection influenced only the migratory response of the ZAS-stimulated cells. 1999 Harcourt Publishers Ltd.

Osteomyelitis and arthrosynovitis associated with Leishmania donovani infection in a dog

A 10-month-old male maremma shepherd dog was presented with chronic diarrhoea, moderate polyuria/polydipsia, lethargy, dysorexia and stiffness. Pain was elicited in the distal parts of all four limbs. Radiographs of the limbs showed increased endomedullary radiopacity and lysis, with thick periosteal proliferations at the metadiaphyseal areas of each radius-ulna and tibia and of the distal metacarpus on one side. Polyclonal hypergammaglobulinaemia was documented and a similar electrophoretic protein pattern was also found in the synovial fluid. Leishmania amastigotes were found in the macrophages in a bone marrow aspirate performed at the level of a distal radius and in a synovial fluid sample obtained from a carpal joint. An indirect immunofluorescence test confirmed the infection. Treatment with N-methyl-glucamine antimoniate was successful and the osteoarticular changes progressively disappeared.