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Biomedical subjects

G D Johnson

Publications and source records attributed to G D Johnson.

At least 127 records · Page 7Linked to original sources
PubMed1985

B-cell production and differentiation in adult rats.

The B-cell development in a group of rats was suppressed for the first 45 days of life by serial administration of rabbit anti-rat IgM and IgD antibody. Total or near total suppression of B lymphopoiesis was achieved. At 45 days, suppression was stopped by injection of IgM and IgD rat paraproteins. The sequence of B-cell and plasma cell development following suppression was assessed by immunohistological analysis of spleen lymph nodes and small intestinal lamina propria. The main findings are listed below. Complete reconstitution of B-cell numbers occurs within 8 days, at which stage germinal centres are also present. B lymphopoiesis in the red pulp of the spleen differs from that reported for bone marrow. Cells develop expressing surface sIgM and sIgM with IgA, but not sIgD. sIgD-positive cells first appear in splenic follicles 2 days after stopping suppression, but their appearance in lymph nodes is delayed until after 3 days. At this stage, sIgD-positive cells become apparent in the splenic red pulp. IgM plasma cells appear from day 4. IgA plasma cells in the gut appear in small numbers at day 6, and gradually increase to normal numbers by day 14. sIgG2c expression in the splenic marginal zone did not approach normal levels, even 2 weeks after suppression was stopped.

Animals↗
PubMed1984

The use of cytocentrifuge preparations for the demonstration of T cell surface antigens.

Cytocentrifuged cell preparations have been evaluated as substrates for the demonstration by immunofluorescence of T cell surface antigens. Results obtained by a 2-stage method with fluorescent conjugate specific for the isotype of the first stage monoclonal antibody, and by a 3-stage procedure employing an intermediate antiserum to mouse IgG as amplifying agent, showed good correlation with those obtained by a standard technique performed on cells in suspension. These methods have the advantages of requiring fewer cells and less antibody and the cytocentrifuge preparations may be stored for batch assay.

Animals↗
PubMed1984

T-cell proliferation and expression of MHC class II antigens.

Two monoclonal antibodies to major histocompatibility complex (MHC) class II antigens, which in combination identify beta chains encoded by the SB and DR loci, were used to investigate which of these gene products were expressed at the cell surface of unstimulated T cells and at various stages of mitogen-induced T-cell maturation. In tests on blood lymphocytes from healthy donors 12% of T cells expressed class II antigens, but only SB antigens were expressed. During activation of T lymphocytes, SB-coded antigens were expressed before DR antigens, and the kinetics of SB expression correlated with the proliferative response of T cells. These results and consideration of recent reports from other laboratories lead us to suggest that SB-coded class II antigens play a role in T-cell proliferation.

Cells, Cultured↗
PubMed1984

Changes in normal polymorphonuclear leucocyte motility after ingestion of IgG aggregates.

Changes in normal polymorphonuclear leucocyte (PMN) motility after membrane-binding and internalisation of IgG aggregates (a model of soluble immune complexes) have been studied by the micropore filter assay. The results have confirmed that IgG aggregates stimulate as well as inhibit PMN chemotaxis. These effects are dependent on the size and concentration of the IgG aggregates in solution as well as the length of time of incubation. Stimulated chemotaxis was observed in a small subset of the whole PMN population which was apparent only when cell distribution through the filters was analysed. These results indicate the need for caution when drawing conclusions about PMN function from results obtained by these assay techniques.

Antigen-Antibody Complex↗
PubMed1984

Impaired polymorphonuclear leucocyte chemotaxis in rheumatoid arthritis.

This study has investigated the chemotactic activity of polymorphonuclear cells (PMNs) isolated from the blood of patients with either articular rheumatoid arthritis (RA) or RA with extra-articular manifestations. A double fluorochrome immunofluorescent staining test has been employed to identify cell-associated immunoglobulins, probably immune complexes. The results suggest an inverse relationship between PMN chemotaxis and staining for cell-associated immunoglobulins, either surface bound or internalised. PMNs from RA patients showed reduced chemotaxis, and this was further reduced when RA PMNs were incubated for 30 minutes in autologous serum. A similar reduction in chemotaxis of normal PMNs occurred after incubation in RA sera. Preincubation of both RA and normal PMNs in RA serum (but not normal serum) resulted in an increase in the number of cells in which cell-associated immunoglobulins were demonstrable. This further reduction in RA PMN chemotaxis after exposure to autologous serum, together with an increase in immunoglobulin staining, may indicate selection of certain PMNs at the time of venepuncture due to cell margination. Such a selection process would call for a re-evaluation of previous studies of RA PMN function in relation to the disease process.

Antigen-Antibody Complex↗
PubMed1983

The IgG subclass responses of human lymphocytes to B-cell activators.

The induction of IgG synthesis by normal human lymphocytes in response to a range of B-cell activators has been studied by indirect cytoplasmic immunofluorescence using monoclonal antibodies to the four IgG subclasses. Considerable variation was found between cells from different donors tested with the same activator but the following trends were observed:- Epstein-Barr virus and Branhamella catarrhalis induced a predominantly IgG3 response, whereas the most prevalent cells in cultures stimulated with lipopolysaccharide and Staph. aureus were IgG2-positive; the subclass distribution obtained with pokeweed mitogen resembled that found in normal serum (IgG1 greater than 2 greater than 3 greater than 4).

B-Lymphocytes↗
PubMed1982

Immunoglobulin inclusions in rheumatoid arthritis polymorphonuclear cells: lack of correlation with circulating immune complexes.

A discriminating direct immunofluorescent test has been used to identify immunoglobulin inclusions in polymorphonuclear leucocytes (PMNs) isolated from the blood of patients with rheumatoid arthritis. These inclusions are thought to represent phagocytosed immune complexes, since normal PMNs incubated in RA sera known to contain raised levels of immune complexes developed similar immunoglobulin inclusions. Inclusions did not develop in normal PMNs incubated in normal serum. No correlation was found between the percentage of either RA blood PMNs with immunoglobulin inclusions or normal PMNs developing inclusions after incubation in RA sera, and levels of immune complexes in the corresponding sera. Using heat-aggregated IgG as a laboratory model of immune complexes, a simple relationship has been demonstrated between the uptake of IgG aggregates by normal PMNs and the concentrations of IgG aggregates in the test solutions over a concentration range of 12.5-200 micrograms . ml-1. These results indicate that the C1q- PEG test gives no measure of the actual amounts of immune complexes available in serum for phagocytosis.

Antigen-Antibody Complex↗
PubMed1982

Differential immunofluorescent staining of polymorphonuclear leucocytes for discriminating between surface bound and internalised immunoglobulin.

Discrimination between immunoglobulin on the surface of polymorphonuclear leucocytes and immunoglobulin internalised as a result of phagocytosis has been achieved by direct immunofluorescent staining with fluorescein and rhodamine antiglobulin conjugates of identical specificity applied sequentially to live cells in suspension and after fixation on microscope slides. Surface bound antigen is recognised by double staining whereas internalised material is stained only by the conjugate applied to the fixed preparation. This differential staining procedure was evaluated in a model system in which normal PMNs were exposed to small (less than 20 s) and large (greater than 90 s) aggregates of human IgG.

Fluorescent Antibody Technique↗
PubMed1982

Anti-ssDNA and antinuclear antibodies in human malaria.

The incidence of serum antinuclear antibodies and serum antibodies to single stranded (ss) and double stranded (ds) DNA was investigated following acute malaria in 58 Caucasians visiting tropical countries but resident in Britain and in 24 Ghanaians resident in Ghana. In Caucasians this infection was associated with a significant increase in the incidence of speckled antinuclear antibodies (38% compared to 3% in controls; P less than 0.001) and a significant rise in antibody levels against ssDNA (14% compared to 5%; P less than 0.05), but no rise in antibodies against dsDNA. Acute malaria in Ghanaians was associated with an incidence of 25% of antinuclear antibodies and 4% of antibodies to ssDNA; these were similar to those found in healthy Ghanaians who are chronically exposed to malaria. Antibodies against dsDNA were not detected. The incidence of antinuclear antibodies and levels of anti-ssDNA antibodies was higher in the Ghanaian healthy population than in normal Caucasians. These observations indicate that malaria is associated with the development of antinuclear and anti-ssDNA antibodies. Ghanaian patients with a tropical splenomegaly syndrome or with a nephrotic syndrome, both of which conditions are suspected of having a malarial aetiology, had serum levels of anti-ssDNA higher than healthy controls. This observation adds further circumstantial evidence to the role of malaria in causing anti-DNA antibodies.

Adult↗
PubMed1981

Binding of wheat gliadin in vitro to reticulum in normal and dermatitis herpetiformis skin.

We have demonstrated by indirect immunofluorescence that wheat gliadin binds in vitro to reticulin-like fibrils present in cryostat sections of human skin, and rat liver, kidney and stomach. Gliadin was seen to bind to fibrils throughout the dermis of both normal and dermatitis herpetiformis skin, and this was particularly striking in the dermal papillae. Serum from 2 dermatitis herpetiformis patients who did not have antireticulin antibody gave reticulin staining when retested by immunofluorescence on cryostat sections of rat tissue pretreated with gliadin. Gliadin treated sections may prove useful in screening patients with gluten sensitive enteropathy for anti-gliadin antibody. Binding of gliadin to skin sites in dermatitis herpetiformis patients and subsequent deposition of antigliadin antibody at these sites may be involved in the development of skin lesions.

Animals↗
PubMed1981

New immunofluorescent blood test for gluten sensitivity.

A new test for the detection of antibodies to gliadin in the sera of children who are gluten sensitive is described. This test is based on the observation that wheat protein binds selectively to connective tissue fibres in cryostat sections of mammalian tissues. Sera containing antibodies to gliadin give a reticulin pattern of staining on section pretreated with wheat gliadin if tested by indirect immunofluorescence. Antibodies to gliadin were detected in this manner in sera fom all of 32 children with coeliac disease, in 16 of whom a provisional diagnosis had been given and in 16 an established diagnosis confirmed by gluten challenge. The incidence of reticulin antibodies detected on untreated sections (in the absence of gliadin) was only 28%. Gliadin antibodies were also present in sera from 15% of 152 children with gastroenterological disorders other than coeliac disease, but most of these non-positive results for coeliac disease were in patients with transient gluten in tolerance, cows' milk-sensitive enteropathy, or Crohn's disease. This new test, although not specific for coeliac disease, promises to be of value as an indicator of gluten sensitivity, and when negative excludes a diagnosis of coeliac disease. It may also be useful in monitoring diet, and in determining when rebiopsy after gluten challenge in appropriate.

Adolescent↗
PubMed1981

Antiperinuclear factor and keratin antibodies in rheumatoid arthritis.

Tests for antiperinuclear factor (APF) demonstrable by indirect immunofluorescence (IF) on smears of human buccal mucosal cells and for antibodies to keratin (AKA) detected on cryostat sections of rat oesophagus were performed on serum from 102 cases of rheumatoid arthritis (RA) and 117 controls. APF was detected in 92% of the cases of RA; positive tests obtained with non-RA sera were generally weaker than those given by the RA group, and the antibody in both RA and non-RA serum was predominantly IgG class. The difficulty in obtaining suitable substrate material previously reported was confirmed, and only 2 satisfactory donors were identified among 27 individuals tested. The incidence of keratin antibodies detected was found to be related to the site from which the tissue was taken; low oesophagus provided the best discrimination between RA and controls (51% and 5% positive respectively), and cardia of the stomach gave the highest incidence of staining in all groups. A laminar staining pattern was seen with most positive sera, but occasionally the keratinised layer was diffusely stained. The presence of AKA showed a marked correlation with both IgM rheumatoid factor and increased Clq binding in RA, but APF did not.

Antibodies↗