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D R Katz

Publications and source records attributed to D R Katz.

At least 55 records · Page 3Linked to original sources
PubMed1995

Tumour necrosis factor-alpha (TNF-alpha) synthesis is associated with the skin and peripheral nerve pathology of leprosy reversal reactions.

Leprosy may be complicated by episodes of increased cell-mediated immunity towards Mycobacterium leprae (reversal reactions) which result in severe local immunopathology in skin lesions and peripheral nerves. Using in situ hybridization and MoAb techniques we have demonstrated TNF-alpha mRNA and TNF-alpha protein in macrophages infiltrating leprosy skin and peripheral nerve. Levels of TNF-alpha mRNA are significantly increased in reactional skin and nerve, particularly in borderline tuberculoid patients. TNF-alpha mRNA and TNF-alpha protein levels are higher in reactional nerves then reactional skin. In both reactional skin and nerve TNF-alpha mRNA is more abundant than TNF-alpha protein; this may reflect the rapid turnover of TNF-alpha protein in an immunologically dynamic situation, such as is seen in reversal reaction. Our findings emphasize the importance of documenting both mRNA and protein production when assessing the role of cytokines in pathology. The leprosy reversal reaction may be regarded as a useful model of tissue immunopathology in which TNF-alpha is generated as part of the host response to infection, but also produces local tissue damage.

Humans↗
PubMed1995

Effect of histone and histone-RNA complexes on the disease process of murine systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is characterised by the production of a variety of autoantibodies against cell surface, nuclear and cytoplasmic antigens. The antigen or antigens responsible for the induction of this disease is/are unknown. We have analysed the antigenicity and pathogenicity of free histones and histones complexed with RNA in Balb/c, B10 Br, C57BL/6 and MRL-lpr/lpr mice by giving 1 microgram and 25 micrograms of each antigen intraperitoneally in complete and incomplete Freund's adjuvant. The same number of control animals were injected with either adjuvant or PBS. In the initial experiment we gave three doses of antigen at three weekly intervals. B10 Brown and C57BL/6 mice had no response to the antigens. Balb/c mice developed a mild transient antibody response against H1 histone, branched peptide of ubiquitinated H2A (peptide T4) and also against ssDNA. However in repeated experiments when the histone-RNA complex was injected into young MRL-lpr/lpr animals at two weekly intervals, a significantly increased antibody response was detected against H1, peptide T4 and some histone peptide residues (204-218 of H1, 1-20 and 65-85 of H2A, 1-25 of H2B, 1-21 of H3 and 1-29 of H4) compared to the control groups. Moreover, this group also showed elevated serum anti-DNA antibody levels and early impairment of renal function assessed by the urine protein levels. These experiments have demonstrated that there is a genetic variation in antibody responses against histones and histone-RNA complexes and that histone-RNA complexes exaggerate the disease in young MRL-lpr/lpr mice by inducing antibodies to basic regions of histones and other autoantigens.

Animals↗
PubMed1994

Transfection of vitamin D receptor cDNA into the monoblastoid cell line U937. The role of vitamin D3 in homotypic macrophage adhesion.

A 2-kB cDNA for the vitamin D receptor (VDR) was cloned in sense orientation into the plasmid pMEP4 (containing a cadmium-inducible metallothionein II promoter and a hygromycin-resistance selection gene) and transfected into monoblastoid U937 cells. The resultant cell line, DH39, expressed two species of VDR mRNA: 4.6-kb wild-type mRNA (present in native U937 cells or cells transfected with pMEP4 alone) and 2-kb transfected mRNA, which increased with cadmium treatment. Binding studies (using the active vitamin D metabolite, 1,25-dihydroxycholecalciferol (1,25-DHCC)) showed that DH39 cells contained five times more VDR per cell than controls, and ten times more after cadmium treatment. DH39 were sensitive to 1,25-DHCC: adding cadmium with 100 nM 1,25-DHCC for 72 h completely inhibited proliferation and induced concomitant differentiation. Unlike control cells, differentiation of DH39 by 1,25-DHCC led to homotypic cell-cell adhesion and formation of macrophage clusters. FACS analysis showed that 1,25-DHCC increased the number of cells expressing CD11b in both DH39 and controls, and the number of cells expressing CD11c in DH39. There was a quantitative increase in mean fluorescence intensity of expression of CD11a and CD18 in DH39. Northern blotting showed increased CD11a and CD18 mRNA in DH39. Ab inhibition of 1,25-DHCC-induced homotypic adhesion showed that CD11a/18 mediated the cell-cell clustering. CD50 expression was decreased on DH39, but the CD11a/18 ligand implicated was CD54. DH39 provides a model system not only for investigating the VDR role in 1,25-DHCC anti-proliferative effects, but also for regulation of homotypic macrophage adhesion mechanisms that are important in disease pathogenesis.

Blotting, Northern↗
PubMed1994

A comparison between cytology and histology to detect anal intraepithelial neoplasia.

INTRODUCTION: Anal intraepithelial neoplasia (AIN), which may be a precursor of anal carcinoma, has been identified on histology following minor anal surgical procedures, in particular the removal of perianal condylomata, in increasing numbers of homosexual and bisexual men. Anal cytology has recently been proposed as a useful method of identifying AIN lesions. OBJECTIVE: To compare anal cytology with histology as a method of detecting AIN. METHODS: 215 homosexual and bisexual men attending a central London sexually transmitted diseases clinic had an anal cytological smear performed under standard conditions. The perianal area and anal canal were then examined using a colposcope, and areas macroscopically suggestive of intraepithelial neoplasia were biopsied. RESULTS: 176 of the 215 patients were biopsied of whom 76 had AIN on histology. 154 of the 215 patients had an adequate anal smear of whom 46 and 85 had cytological features of both HPV and AIN, or HPV alone respectively. Including features of HPV alone as an abnormal smear, anal cytology, when compared with anoscopy and histology as the gold standard for diagnosing AIN, resulted in a sensitivity of 87.5%, a specificity of 16.3%, a positive predictive value of 37.4% and a negative predictive value of 69.6%. Restricting abnormal smears to those with features of both HPV and AIN resulted in a sensitivity of 33.9%, a specificity of 72.5%, a positive predictive value of 41.3% and a negative predictive value of 65.7%. CONCLUSION: Anal cytology is a sensitive but nonspecific method of identifying patients with biopsy proven AIN if cytological features of HPV alone are included as abnormal smears. Specificity is improved by restricting abnormal smears to those with features of both HPV and AIN but this markedly lowers the sensitivity of the test. At present, anoscopy and histology are required in addition to anal cytology to differentiate between patients who simply have anal condylomata and those who also have AIN.

Anal Canal↗
PubMed1994

The role of non-adhesive T-cell-accessory cell interactions in the induction of T-cell proliferative hyporesponsiveness.

We have suggested previously that induction of T-cell proliferative hyporesponsiveness is associated with a defective adhesive T-cell-antigen-presenting cell (APC) interaction. In the previous study, the hyporesponsiveness was allospecific, implying that a T-cell receptor-major histocompatibility complex (MHC) interaction had occurred. Therefore, we hypothesized that this type of non-adhesive T-cell-APC interaction might induce T-cell tolerance rather than activation. This hypothesis has now been tested further in the present study, using two experimental approaches. Firstly, L cells, which express a T-cell receptor ligand, i.e. MHC class II molecules, but lack the capacity to bind to T cells and do not express the crucial receptor/counter receptor lymphocyte function-associated antigen-1 (LFA-1)/intracellular adhesion molecule-1 (ICAM-1) pair, also induced non-allospecific T-cell proliferative hyporesponsiveness; this was not due to any direct inhibitory effect on the T cells. Secondly, monoclonal antibodies (mAb) directed to LFA-1 and ICAM-1 were used to disrupt T-cell-APC adhesion specifically, while allowing for T-cell receptor-MHC interaction to occur. The results of this new study suggest that the non-allospecific T-cell proliferative hyporesponsiveness induced was a function of direct T-cell inhibitory effects of these mAb. Taken together, these experiments add further evidence to support the notion that accessory cells which engage T-cell receptors without providing the necessary co-stimulatory signals induce T cells which are in a state of functional 'paralysis' with respect to the antigen which the T-cell receptor recognizes.

Animals↗
PubMed1993

Effects of the synthetic anti-oxidant, probucol, on the U937 monoblastoid cell line.

Probucol is a clinically important drug that decreases plasma cholesterol in humans and has a marked anti-atherogenic effect in hyperlipidaemic Watanabe rabbits. The action of probucol in this animal model has been partly attributed to its anti-oxidant abilities. Probucol can decrease the oxidative modification of low-density lipoprotein and hence diminish its uptake by macrophages. In this paper, we have examined the effect of probucol on the monoblastic cell line U937 and on U937 cells induced to differentiate towards a macrophage phenotype by 1,25-dihydroxycholecalciferol (DHCC), tumour necrosis factor-alpha (TNF-alpha) or phorbol myristate acetate (PMA). We found that probucol enhanced the proliferation of undifferentiated U937 cells. Probucol also enhanced proliferation in cultures that had been pre-treated with DHCC or TNF-alpha, but had no effect on cultures that had been pre-treated with PMA. In contrast, when U937 cells were treated simultaneously with probucol and DHCC or TNF-alpha, there was a more marked decrease in proliferation than was induced by these agents in the absence of probucol. Probucol had little effect on the phenotype of resultant cells. The surface expression of CD13 (aminopeptidase N), CD4, CD35 (C3b receptor), CD64 (Fc gamma RI), CD71 (transferrin receptor) and HLA Class II was not affected by probucol. Probucol treatment led to a small increase in the surface expression of CD16 (Fc gamma RIII) in TNF-alpha treated cells and to a small decrease in the expression of CD14 (a monocyte marker) in PMA-treated cells. The induction of c-fgr mRNA and TNF-alpha mRNA by DHCC or PMA or TNF-alpha was not significantly altered in the presence of probucol. The affect of probucol on U937 cells does not appear to be due to its anti-oxidant abilities because butylated hydroxytoluene (BHT), an equally powerful anti-oxidant, did not have the same effect on the cell proliferation as probucol and because no changes were detected in the levels of lipid peroxidation in U937 cell culture supernatants.

Antigens, Surface↗
PubMed1993

Retinoic acid induces changes in c-fgr proto-oncogene mRNA levels in Burkitt's lymphoma cells.

The c-fgr proto-oncogene is expressed in Burkitt's lymphoma (BL) cell and cell lines derived from them. When Epstein-Barr virus (EBV)-negative BL cell lines that contain low levels of c-fgr mRNA are infected with EBV, transcription of the c-fgr gene is further induced. In this paper we show that treatment of EBV-negative and EBV-positive BL cell lines with all-trans retinoic acid also stimulates an increase in c-fgr mRNA levels, varying between 2- and 13-fold depending on the cell line. An increase is detectable 12 to 48 h after treatment, depending on the cell line, suggesting that the c-fgr gene is not regulated directly by retinoic acid but responds to other retinoic acid-induced changes in the cell. We also show that treatment of BL cell lines with all-trans retinoic acid either results in a dose-dependent decrease in growth rate, or has no effect on growth, depending on the cell line. It has previously been suggested that the c-fgr gene product might have a role in regulating the growth of BL cells, since treatment of the EBV-positive BL cell line Daudi with alpha-interferon results in a decrease in c-fgr mRNA levels followed by a decrease in growth rate. Our data indicate that there is no general correlation between c-fgr mRNA levels and growth rate in BL cells and so argue against a role for the c-fgr gene product in growth regulation in these cells.

Burkitt Lymphoma↗
PubMed1993

Risk of thrombosis in human atherosclerotic plaques: role of extracellular lipid, macrophage, and smooth muscle cell content.

OBJECTIVE: To assess the size of the lipid pool and the number of smooth muscle cells and monocyte/macrophages in human aortic plaques that were intact and to compare the results with those in aortic plaques undergoing ulceration and thrombosis. DESIGN: The lipid pool was measured as a percentage of the total cross sectional area of the plaque. Immunohistochemistry was used to identify cell types (monocytes/macrophages (M phi) by EBM11 and HAM56, smooth muscle cells by alpha actin). The area of the tissue occupied by each cell type was measured by quantitative microscopy in the peripheral (shoulder) area of the plaque and the plaque cap. Absolute counts of each cell type were expressed as the ratio of SMC:M phi. MATERIAL: Aortas were obtained at necropsy from men aged less than 69 years who died suddenly (within 6 hours of the onset of symptoms) of ischaemic heart disease. 155 plaques from 13 aortas were studied. Four aortas showed intact plaques only (group A, n = 31). Nine aortas showed both intact plaques (group B, n = 79) and plaques that were undergoing thrombosis (group C, n = 45). RESULTS: In 41 (91.1%) of the 45 plaques undergoing thrombosis (group C) lipid pools occupied more than 40% of the cross sectional area of the plaque. Only 12 (10.9%) of the 110 intact plaques (groups A + B) had lipid pools of this size. The mean size of the lipid pool in plaques of groups A, B, and C was 12.7%, 27.3% and 56.7% respectively. Compared with intact plaques those undergoing thrombosis contained a smaller volume of smooth muscle cells (2.8% v 11.8%) and a larger volume of monocyte/macrophages (13.7% v 2.9%) in the plaque cap. The ratio of the number of smooth muscle cells to monocytes/macrophages was 7.8 in group A plaques, 4.1 in group B plaques, and 1.0 in group C plaques. This gradient was the result of an absolute increase in monocyte/macrophages and an absolute decrease in smooth muscle cells. CONCLUSIONS: In the aorta ulceration and thrombosis were characteristic of plaques with a high proportion of their volume occupied by extracellular lipid, and in which there was a shift toward a preponderance of monocyte/macrophages compared with smooth muscle cells in the cap.

Aged↗
PubMed1992

Sensitization of allo-specific T lymphocytes in vivo: role of antigen-presenting cells.

The migratory behavior of antigen-presenting cells was investigated in vivo. Purified murine splenic dendritic cells and splenic and peritoneal macrophages were labelled and injected subcutaneously in the hind foot-pads of mice and monitored for seven days. In the first 24 h, a small quantity of label was recovered from popliteal but not inguinal lymph nodes with radioactive (111In-oxine and 3H-uridine) but not fluorescent (1,1'-dioctadecyl 3,3,3'3'-tetramethylindocarbocyanine perchlorate and fluorescein isothiocyanate) labelling of the antigen-presenting cells. Chemical fixation of the injected antigen-presenting cells had no effect on the detection of label in the popliteal lymph nodes, suggesting that it was unlikely to be due to active cellular migration. Label recovery from hind feet declined with time over the seven day period and was independent of the label type. Essentially the same observations were made whether the antigen-presenting cells were syngeneic or allogeneic to the injected mice and irrespective of the type of antigen-presenting cell used. However, allogeneic antigen-presenting cells, which did not migrate to the draining lymph nodes, successfully primed T lymphocytes in these lymph nodes as shown by a secondary in vitro mixed leukocyte reaction. Again, chemical fixation of the injected antigen-presenting cells had no effect on their ability to prime allogeneic T lymphocytes in the draining lymph nodes. These experiments suggest that, during experimental allo-sensitization via the subcutaneous route, indirect priming of allogeneic T lymphocytes may be a dominant pathway.

Animals↗
PubMed1992

Induction of adjuvant arthritis in mice.

Adjuvant arthritis, induced by injections of Freund's complete adjuvant into the footpads of some rat strains, has been recognized as a useful animal model for many years. There has, however, been notable lack of success in reproducing this model in other species. We now describe the development of adjuvant arthritis in healthy strain mice approximately 2 months after injection of Freund's complete adjuvant. Although the clinical appearance of the mice and the joint histopathology closely resemble the adjuvant arthritis reported in the rat, we were unable to detect rheumatoid factor in sera from the affected animals. In parallel studies of T cell proliferation, affected animals responded to some mycobacterial antigens but not to the 65-kD heat shock protein of Mycobacterium tuberculosis, suggesting that some other epitope is important in the development of the disease.

Animals↗
PubMed1992

Adjuvant composition determines the induction of type II collagen-induced arthritis.

In this study we have investigated the influence of adjuvant composition on the development of collagen-induced arthritis and of anti-collagen type II specific B- and T-cell responses following immunization with type II collagen. DBA/l mice immunized with bovine collagen type II emulsified in complete Freund's adjuvant (CFA) containing Mycobacterium tuberculosis strain H37Ra developed footpad swelling indicative of arthritis. Animals immunized with collagen type II plus CFA containing Mycobacterium butyricum, or incomplete Freund's adjuvant showed no significant increase in footpad width. Induction of anti-CII specific T-cell proliferation was also dependent upon immunization with CII plus CFA containing M. tb H37RA. In contrast, ovalbumin-reactive T-cell proliferation was unaffected by the species of mycobacteria, indicating that the difference in adjuvant activity of the mycobacterial species is specific for anti-collagen type II T-cell responses. Antibody response to collagen type II, unlike T-cell responses, was not significantly different using the two adjuvants. This study therefore demonstrates that murine collagen-induced arthritis requires immunization with collagen type II together with complete Freund's adjuvant containing Mycobacterium tuberculosis H37RA. Since only this combination of antigen and adjuvant induces detectable arthritis and T-cell responses against collagen type II, while antibody synthesis does not have such stringent adjuvant requirements, this suggests that the development of the full pattern of the collagen-induced arthritis disease requires synergistic activation of both humoral and cell-mediated responses.

Adjuvants, Immunologic↗
PubMed1992

The comparative role of 1,25-dihydroxycholecalciferol and phorbol esters in the differentiation of the U937 cell line.

The active metabolite of cholecalciferol, 1,25-dihydroxycholecalciferol (1,25-DHCC), is a mononuclear phagocyte product with immunoregulatory properties which can influence not only surrounding T cells but also other mononuclear phagocytes; and which acts in an autocrine fashion. In this study we have used the U937 cell line as a starting point model to investigate further the comparative role of 1,25-DHCC and phorbol myristate acetate (PMA) upon growth, differentiation and phenotype in the mononuclear phagocyte system, and have correlated our findings with changes in 1,25-DHCC metabolism and receptor expression. Both 1,25-DHCC and PMA inhibit growth and differentiate U937 cells in a dose-dependent fashion. When used together, however, at low doses of PMA, 1,25-DHCC protects against the PMA-induced growth inhibition. At high concentrations of both compounds there is a decrease (1,25-DHCC) or an increase (PMA) in 1,25-DHCC receptor expression, with either 24-OHase (1,25-DHCC) or 1-OHase (PMA) synthesis. If the compounds are used in combination the receptor levels are equivalent to controls, and both enzymes are produced. The phenotype of the 1,25-DHCC-induced cells shows light adherence, class I+, increase in CD4 and CD14 and decrease in CD71. The PMA-induced cell is tightly adherent, class I+, and strongly positive for CD13 with a concomitant decrease in both CD4 and CD71. These findings suggest another role for 1,25-DHCC in the mononuclear phagocyte system, as a potential mitogenic agent. They also suggest that 1,25-DHCC may act at both membrane and nuclear levels within this model of the mononuclear phagocyte pathway and demonstrate one possible way in which physiological peripheral macrophage heterogeneity might be induced, i.e. due to the nature of the signals which are implicated during differentiation. The presence of increased CD4 and decreased CD13 on the surface of 1,25-DHCC-differentiated cells, and vice versa on PMA-differentiated cells, illustrates how this may then be reflected in functional mononuclear phagocyte heterogeneity, which may in turn be reflected in differential peripheral function.

Antigens, Surface↗
PubMed1992

Regulation of c-fgr messenger RNA levels in U937 cells treated with different modulating agents.

The U937 cell line was used to investigate the induction of messenger RNA (mRNA) for the c-fgr mRNA tyrosine kinase proto-oncogene in cells of the monocyte-macrophage lineage. U937 cells were exposed to tumour necrosis factor-alpha (TNF-alpha), TNF-beta and transforming growth factor-alpha (TGF-alpha), alone and in combination with PMA and 1,25-dihydroxycholecalciferol (1,25-DHCC). TNF-alpha and TNF-beta, but not TGF-alpha, decreased the proliferation of U937 cells in a time- and dose-dependent manner, and both TNF-alpha and TNF-beta enhanced the response of U937 cells to PMA during the first 24 hr of treatment and to 1,25-DHCC over 72 hr. TNF-alpha induced a rapid increase in c-fgr mRNA levels within 4 hr, in contrast to slower induction by PMA and 1,25-DHCC. TNF-alpha and 1,25-DHCC together had an additive effect on c-fgr mRNA levels. In U937 cells exposed to PMA, c-fgr mRNA levels continued to increase over 72 hr. Levels of c-fgr mRNA induced by the various modulating agents did not correlate clearly with the changes in proliferation. Therefore, we suggest that although the c-fgr gene product may have a role in differentiation, the more significant role is likely to be in the fully differentiated macrophage.

Animals↗
PubMed1991

Chemically modified antigen-presenting cells induce T lymphocyte allospecific hyporesponsiveness.

We have investigated the interaction between murine T lymphocytes and allogeneic APC in an in vitro proliferative mixed leukocyte reaction. Our results demonstrate that freshly isolated potentially alloreactive murine splenic T lymphocytes, in primary culture, can be induced to develop a state of allospecific proliferative hyporesponsiveness in vitro by exposure to 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide-modified allogeneic APC, a method similar to that previously used to induce nonresponsiveness in murine Ag-specific self-MHC-restricted T lymphocyte clones. This hyporesponsiveness was: specific for the allohaplotype of inducing APC, maintained for 96 h in vitro, not due to cellular inhibitory mechanisms, and associated with reduced ability to secrete IL-2 but not IL-3. Induction of this hyporesponsiveness was not due to altered expression of class II MHC gene products on the APC but was associated with markedly reduced T lymphocyte-APC adhesive interactions despite the lack of a detectable immunophenotypic change in lymphocyte function-associated Ag 1 (LFA-1) and intercellular adhesion molecule 1 (ICAM-1) expression on the modified APC. Therefore, we propose that TCR occupancy in the absence of normal T lymphocyte-APC adhesive clustering may induce T lymphocyte tolerance.

Animals↗