Search PubMed⌕ Search

Biomedical subjects

G A Rook

Publications and source records attributed to G A Rook.

At least 91 records · Page 5Linked to original sources
PubMed1992

The development of monoclonal antibodies to the human mitochondrial 60-kd heat-shock protein, and their use in studying the expression of the protein in rheumatoid arthritis.

OBJECTIVE: To assess the claim that the human 60-kd heat-shock protein (HSP) is highly expressed in the joints of patients with rheumatoid arthritis (RA), but is not readily detected in normal tissues. METHODS: Monoclonal antibodies were raised against the human 60-kd mitochondrial heat-shock protein (P1 protein; hsp60), and their specificity was established. They were then applied to synovial tissue. RESULTS: HSP was expressed similarly in normal, osteoarthritic, and RA synovium. Low levels of hsp60 were detected in synovial fluid by immunoprecipitation. CONCLUSION: Minor differences in the distribution of hsp60 in synovium from RA joints were attributable to increased cellularity and to the disorganization of the tissue architecture.

Animals↗
PubMed1992

Slow bacterial infections or autoimmunity?

In this article, Graham Rook and John Stanford propose that a group of idiopathic diseases that are often associated with a degree of autoimmunity and arthritis, including rheumatoid arthritis, inflammatory bowel disease, sarcoidosis and psoriasis, are caused by extremely slow-growing bacteria. They suggest that these diseases are one end of a continuous spectrum caused by related slow-growing genera, which ranges from rheumatoid arthritis, through Takayasu's arteritis and Whipple's disease, to reach the conventional mycobacterioses such as tuberculosis and leprosy.

Autoantibodies↗
PubMed1992

A model for the investigation of factors influencing haemorrhagic necrosis mediated by tumour necrosis factor in tissue sites primed with mycobacterial antigen preparations.

Mycobacterial lesions and skin sites challenged with soluble mycobacterial antigen are very sensitive to the necrotizing effect of tumour necrosis factor (TNF). We have used a model that permits separate quantitative assessment of swelling and haemorrhage to show that when these reactions are elicited in mice that have not been deliberately immunized, pretreatment of the mice with lipopolysaccharide (LPS), or with a MoAb to CR3 which blocks emigration of myeloid cells into the tissues, will block both the swelling and the haemorrhage. On the other hand, treatment with an inhibitor of platelet-activating factor (PAF), or with misoprostol (a synthetic prostaglandin E1 analogue), or with cobra venom factor (CVF) which depletes complement, preferentially blocks the haemorrhagic component, while leaving the swelling relatively unaltered. As swelling occurs before the haemorrhage is seen, it is possible that these factors act at a late stage in the cascade of events leading to the tissue damage. However, LPS and CVF were able to inhibit swelling and haemorrhage in the massive reactions elicited in pre-immunized animals, whereas the PAF inhibitor had no detectable effect.

Animals↗
PubMed1992

Agalactosyl IgG in pristane-induced arthritis. Pregnancy affects the incidence and severity of arthritis and the glycosylation status of IgG.

The effect of pregnancy on the incidence and severity of pristane-induced arthritis was examined along with the glycosylation status of IgG during the ante-natal and post-partum periods. It was found that pristane-induced arthritis is prevented by pregnancy. In addition, the levels of agalactosyl IgG fall during pregnancy but rise to greater than normal within a few days of parturition, before resetting towards the norm shortly afterwards. Interestingly, the level of agalactosyl IgG correlates with the severity of arthritis. As previously reported IL-6 may be an important factor, not necessarily the only one, in the production of agalactosyl IgG. Here it is clearly demonstrated that the kinetics of IL-6 activity post-pristane injection parallels the kinetics of agalactosyl IgG production. In addition, the overshoot in agalactosyl IgG levels immediately post-partum coincides with a burst in IL-6 activity. It is considered that these changes in IgG glycoform levels, or the factors which control them, may be related to the mechanisms underlying prevention/remission of arthritis during pregnancy.

Animals↗
PubMed1992

Increased levels of prolactin during, but not after, the immunisation with rat collagen II enhances the course of arthritis in DBA/1 mice.

In addition to its well known effects on reproductive organs and lactation the pituitary hormone prolactin (PRL) also influences immune functions. The present investigation was performed in order to clarify the regulatory role of prolactin in autoimmune disease by using the collagen II arthritis model. Groups of virgin female DBA/1 mice were subjected to different short-term treatment protocols (5-10 days) with rat PRL and the drugs bromocriptine (inhibits prolactin secretion) and haloperidol (enhances prolactin secretion). Treatments were performed at different stages of disease development, and effects on clinical scores, anti-collagen II antibody titres as well as agalactosyl IgG levels were recorded. The effects of the treatment protocols on serum PRL levels were assessed by using a radioimmunoassay (RIA) system. Although the accumulated results of the present study indicate that PRL does not fulfil a major role in the regulation of collagen II arthritis, some interesting observations were made. High levels of PRL (PRL injections) made the arthritis worse only if treatment was performed during the induction stage of the disease. Bromocriptine treatment during the immunisation period did not significantly affect the course of arthritis, but treatment at later stages tended to cause exacerbation (significant at the onset period only). These results indicate that PRL has different effects during early and late stages of the development of collagen II-induced arthritis.

Animals↗
PubMed1992

Relationship between interleukin 6, agalactosyl IgG and pristane-induced arthritis.

IL-6 titres in sera and peritoneal exudate fluids (PEF) derived from pristane injected DBA/1 and CBA/Igb mice were measured. Arthritic DBA/1 mice had significantly higher serum IL-6 titres than nonarthritic or normal mice at 160 days post pristane injection. By contrast, although both arthritic and non-arthritic CBA/Igb mice had higher serum IL-6 titres than normal mice, there was no significant difference in serum IL-6 titre between these two groups at day 200-230. In both strains of mice, the IL-6 titres in PEF were more than 10 times serum levels regardless of arthritis. As previously reported for CBA/Igb mice, agalactosyl IgG levels are raised in pristane injected DBA/1 mice and the percentage is higher in arthritic animals than that in non-arthritic mice. An association between serum agalactosyl IgG levels and PEF IL-6 in pristane injected DBA/1 was demonstrated. Moreover, the injection of recombinant IL-6 into normal mice increased their serum agalactosyl IgG levels. However, it is considered that IL-6 is not the only factor involved in the production of agalactosyl IgG.

Animals↗
PubMed1992

Tumour necrosis factor production by alveolar macrophages in pulmonary sarcoidosis and tuberculosis.

Tumour Necrosis Factor alpha (TNF/Cachectin) is a cytokine produced mainly by macrophages, which has been shown to cause endothelial cell damage, pyrexia and weight loss, clinical features of tuberculosis, but not of sarcoidosis which is in many other respects a similar disease. 1,25 di-hydroxy Vitamin D and gamma interferon, factors which are present in vivo in both tuberculosis and sarcoidosis, enhance the ability of macrophages to release TNF in vitro. We have studied the ability of pulmonary alveolar macrophages (PAM) harvested by broncho-alveolar lavage (BAL) to produce TNF in response to stimulation with E. coli endotoxin lipopolysaccharide (LPS). 25 patients undergoing bronchoscopy and BAL were studied: 9 with sarcoidosis, 7 with tuberculosis (TB) and 9 (non-neoplastic) disease controls. TNF was assayed by Enzyme Linked Immunosorbent Assay (ELISA) in lavage fluid and cell culture supernatants. No TNF was detected in lavage fluid from any of the groups. PAMs from control patients released no detectable TNF spontaneously, but released 59 +/- 31 units after LPS stimulation. Cells from patients with sarcoidosis and tuberculosis released TNF spontaneously in vitro (TB 226 +/- 106 units; Sarcoidosis 293 +/- 176). TNF release by these cells was not increased further by addition of an optimal concentration of LPS. Thus, the pulmonary macrophages of patients with sarcoidosis and tuberculosis released significantly more TNF than those of controls.

Adult↗
PubMed1992

The effect of Mycobacterium tuberculosis on the susceptibility of human cells to the stimulatory and toxic effects of tumour necrosis factor.

It has previously been shown that the inherently tumour necrosis factor-alpha (TNF-alpha)-sensitive L929 murine fibroblast cell line becomes much more sensitive to the cytotoxic effect of this cytokine after exposure to Mycobacterium tuberculosis in culture. In this study it is now shown that normal human cells of types likely to be involved in tuberculous lesions are affected in a similar way. Growth of normal human fibroblasts is usually stimulated by TNF-alpha in vitro, but after exposure to M. tuberculosis or to extracts of this organism, these cells are killed rather than stimulated by subsequent exposure to TNF-alpha. Similarly, human endothelial cells become susceptible to doses to TNF-alpha which do not normally affect viability. Moreover this enhancement of sensitivity to TNF-alpha is not confined to its toxicity. Endothelial cells and HeLa cells exposed to M. tuberculosis express increased levels of ICAM-1 after subsequent exposure to TNF-alpha, implying synergy between the two stimuli. It is suggested that these effects contribute to the ability of M. tuberculosis to distort the normal protective role of TNF-alpha so that the cytokine becomes detrimental to the host.

Cell Adhesion Molecules↗
PubMed1991

Cytokines and the Koch phenomenon.

We outline the mechanisms contributing to the human form of the Koch phenomenon, which we define as necrosis occurring within 24-48 h of injection of mycobacterial antigen into the skin of past or present tuberculosis patients. It is probable that tissue damage mediated in the same way occurs in the lesions themselves. We suggest that the necrosis is mediated in part by cytokines, particularly Tumour Necrosis Factor (TNF), and that this occurs for three reasons. First, Mycobacterium tuberculosis evokes an immunoregulatory abnormality characterised by raised agalactosyl IgG. This abnormality, also found in rheumatoid arthritis, Crohn's disease, and Erythema Nodosum Leprosum, seems to be associated with dysregulation of cytokine release. Secondly, M. tuberculosis itself triggers further cytokine release. Thirdly, the normally protective role of TNF is distorted by several interacting properties of components of M. tuberculosis, which render the cytokine toxic to the host tissues. The immunoregulatory abnormality may be susceptible to correction by immunotherapy.

Humans↗
PubMed1991

Changes in IgG glycoform levels are associated with remission of arthritis during pregnancy.

It was found that the percentage of IgG-associated agalactosyl N-linked oligosaccharides (G0) falls during normal human pregnancy and rises to values higher than before conception following delivery (n = 10, 39-55 days after delivery). Serial bleeds from a normal pregnant woman showed a fall in the percentage G0 during gestation and a rapid rise post-partum. A similar study on a pregnant arthritic woman with a pathologically elevated percentage G0 also showed a fall in percentage G0 during pregnancy and a rapid rise post-partum. The changes in IgG glycosylation in the pregnant arthritic woman occurred simultaneously with the pregnancy-induced remission and post-partum recurrence of disease. A further seven pregnant women with rheumatoid arthritis were studied and analysis of their G0 values pre- and post-partum confirmed the result. In a further series of experiments using an animal model of rheumatoid arthritis, DBA/1 mice with collagen-induced arthritis were found to have elevated G0 levels compared with control mice. The percentage G0 was found to fall simultaneously with pregnancy-induced remission to the same value as non-arthritic pregnant mice. Post-partum recurrence of arthritis in these mice was also accompanied by a simultaneous and rapid rise in percentage G0. Pseudopregnancy did not result in a change in the percentage G0, confirming the effect of true pregnancy. Since the proportion of agalactosyl IgG is abnormally high in the serum of patients with rheumatoid arthritis these changes in IgG glycoform levels, or the factors which control them, may be related to the mechanisms underlying remission of arthritis in humans during pregnancy.

Acetylglucosamine↗
PubMed1991

Maintained pregnancy levels of oestrogen afford complete protection from post-partum exacerbation of collagen-induced arthritis.

Pregnancy is known to influence the course of rheumatoid arthritis (RA) in women, as well as type II collagen-induced arthritis (CIA) in DBA/1 mice. A characteristic feature is the remission during gestation and the exacerbation of the diseases during the post-partum period. In the case of CIA in DBA 1 mice, two hormonal changes have been assumed to be critical for the induction of the post-partum flare: (i) the fall in steroid hormone levels from those present during pregnancy; and (ii) surges of prolactin (PRL) release at and after delivery. Our results show that treatment with oestradiol during a short period immediately after parturition protects the mouse from a post-partum flare of the disease, and that treatment with bromocriptine, a drug known to inhibit the endogenous PRL release, has a significant though less marked effect. Studies of lactating (i.e. animals with physiological stimulation of endogenous PRL release) and non-lactating arthritic mice revealed no clear-cut differences, indicating that PRL is of minor importance for the induction of the post-partum flare. Some steroids other than oestradiol, which may be implicated in the exacerbation of arthritis, namely progesterone and hydrocortisone, had no clinical effect. Analyses of agalactosyl IgG levels in mice with CIA, and anti-collagen II antibodies in sera collected at the end of the experiments revealed no significant differences between the oestradiol and the control groups. The successful oestradiol treatment of the mice indicates that the drop in endogenous oestradiol levels prior to delivery ends the oestrogen-mediated protection against arthritis during pregnancy.

Animals↗
PubMed1991

Effect of mycobacteria on sensitivity to the cytotoxic effects of tumor necrosis factor.

Unlike Mycobacterium leprae, Mycobacterium tuberculosis is not found inside cells other than macrophages and polymorphonuclear cells in vivo, yet previous work has revealed that in vitro it readily enters all cell lines tested. Moreover, these cells are not killed by the intracellular mycobacteria. We report here that when fibroblasts take up live (but not killed) M. tuberculosis H37Rv, they develop greatly increased sensitivity to the toxic effects of tumor necrosis factor (TNF) whether the cell line is inherently sensitive to TNF or not. Ultrasonically disrupted M. tuberculosis also has this property. The increased sensitivity is seen in the absence of metabolic inhibitors, although addition of emetine, an inhibitor of protein synthesis, causes the effect to manifest itself earlier and at a lower concentration of TNF. In contrast, infection with Mycobacterium bovis bacillus Calmette-Guérin induces little or no increased sensitivity to TNF, whereas Mycobacterium avium and M. tuberculosis H37Ra have intermediate sensitivities. We discuss the possibility that virulent tuberculosis strains produce a factor which distorts the normal protective function of TNF, rendering it toxic to host tissues and leading to the classical immunopathology of tuberculous lesions.

Animals↗
PubMed1991

Genetic and immunological analysis of Mycobacterium tuberculosis fibronectin-binding proteins.

Recombinant phage clones, TB1 and TB2, were selected from a Mycobacterium tuberculosis lambda gt11 DNA expression library by screening with a polyclonal antiserum raised against the antigen 85 complex of Mycobacterium bovis BCG. Analysis of recombinant DNA inserts and expressed fusion proteins showed that two new genes had been isolated. The product of clone TB2 was identified as a member of the 30/31-kDa antigen 85 complex. Restriction enzyme analysis showed that this gene differs from previously cloned members of this antigen complex, with detailed serological analysis indicating that it may encode the 85C component. Antisera raised against the expressed product of clone TB1 recognized a 55-kDa protein in M. tuberculosis extracts. The 55-kDa protein also has fibronectin-binding activity and, like the 30/31-kDa family, is a prominent target of the antibody response in patients with mycobacterial disease. Although the clones were selected by using the same antiserum, detailed analysis by serology and by DNA hybridization showed that they represent two quite distinct types of fibronectin-binding activities expressed by M. tuberculosis. Further analysis of the fibronectin-binding antigens of M. tuberculosis may provide important insights into their role in mediating the interaction with the host immune system.

Antibodies, Monoclonal↗
PubMed1991

New insights into the immunopathology of tuberculosis.

Tuberculosis is characterised by fever, weight loss and necrosis in both lesions and tuberculin skin test sites (Koch phenomenon), although the antigens of Mycobacterium tuberculosis are not directly toxic to the tissues. The tissue damage appears to be due to several interacting factors. First, M. tuberculosis induces an immunoregulatory disorder of which a raised percentage of agalactosyl IgG is a marker. This is seen also in rheumatoid arthritis and Crohn's disease and is associated with tissue-damaging inflammation. Subsequently, several properties of M. tuberculosis exacerbate this disorder by triggering cytokine release, and rendering tissues sensitive to the toxicity of tumor necrosis factor (TNF). Moreover, M. tuberculosis, but not bacillus Calmette-Guérin or several Mycobacterium avium strains, produces a factor which increases the toxicity of TNF for individual cells. Thus, M. tuberculosis may distort the normal protective role of TNF so that this cytokine becomes toxic to the host. The immunoregulatory disorder associated with agalactosyl IgG appears to be susceptible to immunotherapy, so novel types of treatment for the immunopathological component of tuberculosis are being explored.

Animals↗