PubMed Health⌕ Search

Biomedical subjects

R Johnstone

Publications and source records attributed to R Johnstone.

29 records · Page 2Linked to original sources
PubMed1991

Analysis of the IgG subclass production from rheumatoid arthritis synovial cell cultures.

In man there are four subclasses of IgG which differ from each other with respect to their biological properties. Some evidence suggests that the production of IgG3 is unusually high in rheumatoid synovia. In this study secretion of IgG subclasses by synovial lymphocytes in vitro was measured using sensitive subclass-specific ELISAs. It was found that, in both synovial membrane- and synovial fluid-derived cell cultures, the general pattern of IgG subclass secretion was IgG1 greater than 2 greater than 3 greater than or equal to 4, and that, in most cultures, IgG3 was a minor subclass accounting, on average, for only 8% of the total IgG. This was similar to the percentage of this subclass in normal human serum and in culture supernatants from the patients' peripheral blood lymphocytes.

Arthritis, Rheumatoid↗
PubMed1990

The frequency of mouse spleen dendritic cells which present alloantigens or ovalbumin to primed T lymphocytes is equal.

We have used limiting dilution analysis to compare the frequency of dendritic cells (DC) which present endogenous alloantigens with that which present an exogenous protein antigen to T lymphocytes. Spleen DC present alloantigens or ovalbumin to primed T lymphocytes with equal frequency, showing that DC are equipotent for presenting endogenous and exogenous antigens. Also, antigen-presenting cell (APC) frequencies among DC were compared with other APC populations. DC were enriched about 1000-fold for APC compared to unfractionated spleen cells.

Animals↗
PubMed1990

Immunoglobulin G subclasses secreted by human B cells in vitro in response to interleukin-2 and polyclonal activators.

The IgG subclasses secreted by human B cells in vitro in response to IL-2 have been analysed. B cells were prepared from tonsil, blood and spleen, and cultured with recombinant IL-2 in the presence or absence of two polyclonal activators: Staphylococcus aureus Cowan 1 (SAC) and bacterial lipopolysaccharide (LPS). Secretion of all four subclasses and of IgM was stimulated by IL-2, but the relative amounts varied according to (i) the tissue source of the B cells, and (ii) which polyclonal activator was used. The amount of IgG1 tended to be higher and IgG2 tended to be lower when SAC was the polyclonal activator (compared to LPS). This difference was most marked for tonsil B cells, and it was found that SAC had a negative effect on secretion of IgM and IgG2 in these cultures, whilst synergizing with IL-2 to stimulate the production of IgG1, 3 and 4. When the degree of stimulation of different pairs of isotypes was analysed, several interesting positive correlations emerged. In tonsil B-cell cultures, stimulation of IgM and IgG2 was linked with each other, but not with IgG1, whilst in blood B-cell cultures all isotypes appeared to be stimulated co-ordinately. Stimulation of IgG1 and IgG3 were positively correlated in cultures of B cells from all tissues. The results emphasize that the effects of a single cytokine on immunoglobulin isotype production can be influenced by the source of the B cells, and by other signals delivered to the cells.

Antigens, Bacterial↗
PubMed1987

A limiting dilution assay to determine the frequency of antigen presenting cells.

A limiting dilution assay to measure the functional frequency of antigen presenting cells (APC) has been developed and used to measure the frequency of mouse lymphoid cells which stimulated the mixed leucocyte response. The experiments utilised measurements of proliferation in 20 microliter hanging drop microcultures of activated T lymphocytes. When the data supported a model of single-hit kinetics, the APC frequency in the titrated stimulating cell population was calculated by the method of maximum likelihood. The assay was validated by measuring the frequency of unpurified spleen cells and enriched spleen dendritic cells which presented alloantigens in mixed leucocyte culture. APC frequency in unpurified spleen cells was 1:7254 (SE +/- 2134, 8 experiments) and was increased markedly to 1:15 (SE +/- 7, 7 experiments) when enriched populations consisting 70-95% of dendritic cells were used as stimulators.

Animals↗
PubMed1987

Transplanted isolated hepatocytes: effect of partial hepatectomy on proliferation of long-term syngeneic implants in rat spleen.

Proliferation of isolated hepatocytes in long-term splenic implants was assessed by flash labelling with a 1 pulse of tritiated thymidine (3H TdR). Cell kinetics showed that the basal labelling index was 0.9% which was greater than normal non-regenerating liver. Twenty four hours following partial hepatectomy the labelling index was 2.0%, a significant rise. These results suggest that hepatocytes transplanted to the spleen constitute a suitable model for screening putative hepatotrophic factors, and are of relevance in establishing clinically useful models of hepatocyte transplantation.

Animals↗
PubMed1986

Human serum does contain a high molecular weight hepatocyte growth factor: studies pre- and post-hepatic resection.

Levels of a high molecular weight hepatotrophin were measured in human serum taken from patients before and 24 hours after undergoing major hepatic resection. In in-vitro rat hepatocyte cultures a 'hepatotrophin' enriched fraction of human serum induced the incorporation of tritiated thymidine into DNA in both pre and post-operative patients. Levels after hepatic resection were 2-3 fold higher than those achieved at the same protein concentration before operation in the same patient. The hepatotrophic factor had an apparent molecular weight of approximately 150,000 daltons, and was an anionic protein.

DNA↗
PubMed1986

Observations on rat spleen reticulum during the development of syngeneic hepatocellular implants.

August rat hepatocytes isolated by collagenase perfusion were implanted directly into the spleens of syngeneic recipients. Graft development was monitored by a combination of staining techniques and when surviving hepatocytes were difficult to recognize by routine histology, indirect immunofluorescence permitted their rapid identification. Liver cells were found up to 21 months after transplantation, thus confirming the ability of the spleen to support hepatocellular grafts. The reticular framework of the spleen appears to play an important role. The reticulum mesh of the red pulp traps injected cells and there is rapid generation of reticulum fibres around them within 4 days. The subsequent proliferation and organization of liver cells into recognizable hepatic plates, glandular rosettes and acini was accompanied by the development of a rich and distinctive reticular scaffold with a pattern resembling that of regenerating splenic tissue.

Animals↗
PubMed1984

Selective externalization of the transferrin receptor by sheep reticulocytes in vitro. Response to ligands and inhibitors of endocytosis.

The transferrin receptor of sheep reticulocytes is released in vesicular form during in vitro incubation of the reticulocytes. A polyclonal antibody against the transferrin receptor slows down the release of the vesicles bearing the receptor, whereas transferrin and calf serum accelerate vesicle release. Vesicle formation and receptor release are inhibited at low temperatures and by the presence of inhibitors of ATP formation. In addition, lysosomotropic agents or transglutaminase inhibitors block receptor externalization. The externalized receptor has the same molecular size and peptide map as the receptor isolated from the membrane, suggesting that an intact receptor is removed and released from the cell. An unidentified peptide of 70 kDa is externalized with the transferrin receptor. Peptide maps show that the 70-kDa species is not a degradation product of the receptor. No function has yet been assigned to the 70-kDa peptide.

Acyltransferases↗
PubMed1980

Advantages of low dose steroid from the day after renal transplantation.

We have used a low dose of steroid (20 mg of prednisolone), commencing the day after transplantation, for 151 consecutive renal transplants in 141 patients. Five patients received grafts from living related donors, 146 received cadaver grafts. All patients received azathioprine for routine immunosuppression and the first 47 received a single dose of actinomycin C i.v. for treatment of rejection. No other immunosuppressive drugs were used. This treatment provided satisfactory immunosuppression as 109 of 151 grafts continue to function for periods of 3 months to 10 years and, of 42 grafts lost, only 17 failed from rejection. The cumulative survival of first cadaver grafts at 1 and 2 years in recipients of all ages (7 to 55 years) was 77.9 and 76.0%, respectively; in recipients 15 to 34 years old, 90.9 and 86.1%, respectively. Twenty-three patients died, no patient died from infection during the admission for transplantation, and infection played a part in the deaths of only four patients. The incidence of other complications was low; seven patients developed gastrointestinal complications, one died, four patients developed diabetes, all survived; only one patient developed avascular necrosis of bone.

Administration, Oral↗