PubMed Health⌕ Search

Biomedical subjects

P L Amlot

Publications and source records attributed to P L Amlot.

At least 19 recordsLinked to original sources
PubMed1991

Monoclonal antibody treatment in rheumatoid arthritis: the clinical and immunological effects of a CD7 monoclonal antibody.

Six patients with rheumatoid arthritis were treated with a CD7 mouse monoclonal antibody, RFT2, daily for 15 days. Only two patients had a significant improvement in clinical disease activity which lasted 7-14 days. No serious adverse effects occurred although all patients developed antibodies against mouse immunoglobulin. During treatment T-lymphocyte numbers decreased and T-lymphocyte CD7 expression was absent in all but one patient.

Adult↗
PubMed1991

The effect of a chimeric mouse-human CD7 antibody on human T, natural killer, and lymphokine-activated killer cell activity in vitro.

A chimeric CD7 antibody has been constructed with mouse variable and human constant regions and is currently being assessed in the prophylaxis of renal graft rejection. In this study we have investigated if this antibody or its murine parental form inhibits the function of a number of immune effector mechanisms involved in host defense against infection and/or malignancy. Most memory T cells and all natural killer cells express the CD7 antigen and could therefore be affected by CD7 antibody. Murine and chimeric CD7 antibodies significantly inhibit the alloproliferation of naive (65 +/- 4% and 66 +/- 8%, respectively) but not memory T cells (86 +/- 2% and 98 +/- 4%, respectively) in a primary mixed lymphocyte reaction relative to the negative control CD10 antibody (P less than 0.001). The memory T cell proliferative response to recall antigen is also largely unaffected by murine and chimeric CD7 antibodies relative to the negative control antibody (91 +/- 12% and 103 +/- 10%, respectively). The CD7 antigen is almost completely modulated from the surface of NK cells after incubation for 24 hr with either the murine or chimeric CD7, but not the CD10, negative control. The modulation of CD7 antigen by antibody, however, does not affect the cytotoxic function of either the NK or lymphokine-activated killer cells significantly. Preincubation with the chimeric antibody however, consistently showed a small inhibition relative to the negative control of 75-80% in NK assays and to 80-90% in LAK assays. These data suggest that both murine and chimeric CD7 antibodies may have a selective effect on alloproliferation but may largely spare a major component of the host's innate immunity as well as memory T cell proliferation to previously encountered antigens.

Antibodies↗
PubMed1990

Inhibition of alloresponsive naive and memory T cells by CD7 and CD25 antibodies and by cyclosporine.

Human naive and memory T cells can be isolated from each other by their CD45RA and CD45RO expression, respectively. This enables the assessment of their differential sensitivities to immunosuppressive agents for the first time. We have investigated the ability of cyclosporine or CD7 and CD25 antibodies to selectively block alloantigen stimulated naive and memory T cells in vitro. CD7 antibodies blocked the proliferation of naive (P less than 0.025) but not memory T cells in a primary MLR. CD25 antibody inhibited both naive and memory subsets but a significantly greater effect was found on the memory T cells (P less than 0.005). The constitutive CD7 and CD25 antigen expression on resting naive or memory T cells was related to the inhibitory activities of these antibodies on both subsets. Accordingly, naive T cells expressed more CD7 antigen than memory cells while memory T cells displayed low levels of CD25 antigen that was absent from naive populations before activation. Cyclosporine, like CD25 antibody, inhibited both subsets in a primary MLR but had a greater effect on memory cells (P less than 0.02). Memory T cells, therefore, are more dependent than naive cells on IL-2 for proliferation. There was great individual variation in the ability of CsA to block the MLR. The simultaneous addition of CD25 or CD7 antibody together with CsA, however, enhanced the MLR inhibition as the effects of all three were additive. This suggested interference by these agents at different points during T cell activation. Thus, in CsA sensitive individuals, one-tenth of the optimal CsA concentration together with CD25 antibody maintained maximum immunosuppression in vitro. These results demonstrate the possibility of using CD7 and CD25 antibodies for selective inhibition of naive or memory T cells and also the possibility of augmenting the inhibition of and reducing the CsA concentration required for clinically effective immunosuppression.

Antibodies, Monoclonal↗
PubMed1990

The development of primed/memory CD8+ lymphocytes in vitro and in rejecting kidneys after transplantation.

In normal individuals, 80 +/- 5% of circulating CD8+ T cells express CD45RA, and 20 +/- 7% of these cells express CD45R0 antigens. After activation, CD8+ cells expressing CD45RA decrease to 56-67% while those expressing CD45R0 increase to 38-67%. Although precursors of alloantigen-specific cytotoxic T cells were found in both CD8+, CD45RA+ and CD8+, CD45R0+ subsets, the specific effector cells were exclusively CD8+, CD45R0. Allospecific cytotoxic CD8+ clones were also entirely CD45R0+. A lectin-dependent cytotoxic (LDC) assay unmasked a hierarchy of killing after alloactivation which was CD8+, CD45R0+ greater than CD8+, CD45RA+ greater than CD4+, CD45R0+ greater than CD4+, CD45RA+. The phenotype of CD8+ T cells in rejecting kidneys was similar to in vitro alloantigen-activated CD8+, CD45R0+ cells and cytotoxic CD8+ clones. Firstly there was an increase in the relative proportions of CD45R0+ (60 +/- 8%) and a decrease in CD45RA+ (35 +/- 10%) CD8+ cells relative to circulating CD8+ subsets. In the rejecting grafts, 34 +/- 9% of the CD8+ cells were also DR+ indicative of recent activation. Furthermore, 16% (range 4-35%) of rejecting CD8+ cells were Ki67+ suggesting that these cells were proliferating. Finally, 17% (range 4-53%) of T cells in rejecting kidneys simultaneously expressed both CD45RA and CD45R0 markers. These results show that in vitro alloantigen-activated CD8+, CD45R0+ cells represent a primed/memory cytotoxic population. In addition, they provide indirect evidence that a proportion of CD8+ cells in rejecting kidneys were actively switching from a naive to a memory phenotype in vivo in a manner analogous to that in vitro.

Antibodies, Monoclonal↗
PubMed1990

Distinctive development of IgG4 subclass antibodies in the primary and secondary responses to keyhole limpet haemocyanin in man.

The human primary and secondary IgG subclass antibody responses to keyhole limpet haemocyanin (KLH) have been measured by ELISA using IgG subclass-specific monoclonal antibodies. KLH-specific IgG1 and IgG2 antibodies were detected 3 weeks after primary immunization, and IgG1, IgG2 and IgG4 antibodies after secondary immunization. IgG3 antibodies were observed less frequently in both primary and secondary responses. Unlike the other subclasses, IgG4 antibodies developed very slowly during the primary response, with no antibody detected at 3 weeks and often with only low titres 1 year after immunization. In one individual, this IgG4 primary response peaked around 10 months, but there was considerable variation between individuals. Comparing primary and secondary responses, the greatest increase in KLH antibody was for the IgG4 subclass (45-fold rise), followed by IgG1 (7.3-fold rise), whilst IgG2 and IgG3 KLH-specific antibodies did not show a significantly increased secondary response. There was no detectable IgG4 antibody response when secondary immunization was performed 1 month after the primary, even though IgG1, IgG2 and IgG3 antibodies were present. Reasons for the different time-course of IgG4 anti-KLH development and the isotype-related differences in 'memory' responses are discussed.

Adult↗
PubMed1990

Antibodies of different human IgG subclasses show distinct patterns of affinity maturation after immunization with keyhole limpet haemocyanin.

The functional affinities of antibodies of different IgG subclasses were measured in normal individuals during the primary, secondary and tertiary immune responses to keyhole limpet haemocyanin (KLH). IgG1 responses showed marked affinity maturation between Days 7 and 21 after primary and by Day 7 after secondary and subsequent immunizations, correlating with an expansion of high-affinity antibody populations. When present, IgG2 responses were of low titre but high functional affinity with no change in response to immunization and may represent a T-independent cross-reacting response with a carbohydrate epitope of KLH. IgG3 responses were variable but generally of low titre and low functional affinity, although those of higher titre and affinity were associated with secondary delayed-type hypersensitivity (DTH) and clinical reactions to KLH. In contrast to IgG1, IgG4 antibodies were not detected until 1 year after primary immunization, when they were found at low titre but high functional affinity. Following secondary immunization, IgG4 titres increased rapidly but without any further increase in affinity. The emergence of high-affinity IgG4 antibodies coincided with a loss of the high-affinity IgG1 populations, suggesting a preferential switch with time from high-affinity IgG1 antibodies to IgG4.

Adult↗
PubMed1989

Characterization of a human T cell-specific chimeric antibody (CD7) with human constant and mouse variable regions.

A chimeric human-mouse anti-T lymphocyte mAb (CHT2; SDZ 214-380) has been constructed by cloning the variable region exons of both the L and H chains from the murine hybridoma RFT2 which have CD7 specificity and reactivity with a 40-kDa Ag. The variable L chain exon was joined to the human C kappa, and the variable H chain exon was joined to the human IgG1 region exon encoding the human allotype nGlm(z), nGlm(a). The gene constructs were introduced by electroporation into SP2/0, a non-Ig-producing murine myeloma. The identical tissue reactivity of the newly made CHT2 and the original murine RFT2 mAb (CD7) was confirmed by blocking experiments as well as by immunohistology and flow cytometry. Because this new mAb may have clinical use, the CD7 Ag expression of T lineage cells has also been quantitated in double and triple immunofluorescence assays in combinations with mAb to restricted forms of leukocyte common Ag that designate unprimed (CD45R+) and primed T lymphocyte populations (UCHL1+). CHT2 shows very strong reactivity with large thymic blast cells and cortical thymocytes from which T-ALL originates. Strong staining is seen on CD45R+ unprimed "virgin" T lymphocytes, whereas the expression on UCHL1+ primed "memory" cell types is weaker unless these cells are reactivated by mitogens or Ag. Thus CHT2 may spare a substantial population of resting memory T cells which is relevant to its potential therapeutic use. In addition the chimeric antibody had a greater in vitro antibody dependent cytotoxicity and a prolonged half-life (4.2 to 5.0 days) in Rhesus monkeys.

Amino Acid Sequence↗
PubMed1989

The expression of T cell receptor-associated proteins during T cell ontogeny in man.

The expression of TCR-associated molecules was examined in human fetal and postnatal tissues. From gestational wk 7 onward in the fetal liver, putative prothymocytes have been identified with cytoplasmic CD3 positivity (cCD3+). These immature cells are TdT- and do not express membrane CD3 (mCD3-) or TCR beta identified by beta F1, but show CD7 and CD45 positivity without CD1, CD2, CD5, CD4, CD8, CD10, and class II Ag. Their high proliferative activity is indicated by greater than 85% Ki67 positivity. After the 10th wk, beta F1+, mCD3+ cells also appear in the liver and these are mostly Ki67- but no TCR gamma delta-bearing cells can be identified at such an early stage of extrathymic development. In the mCD3- TdT-fetal thymus (10 1/2 to 18th wk) cCD3+, mCD3- CD1-blasts proliferate (Ki67+) and lack TCR-beta or TCR-gamma delta. The TdT-, CD1+ cortical thymocytes develop into TCR-beta + and WT31-positive (TCR-alpha beta +) cells. Subsequently TdT-positive thymocytes become detectable around 19 to 20 wk, and in such glands the peak of proliferative activity is seen among TdT+, cCD3+ cells which appear to acquire, in a regular sequence, cytoplasmic beta F1 (TCR-beta), mCD3, and TCR-alpha beta (WT31 positivity) together with the loss of TdT and Ki67 positivity. A newly described transitional population of cells is TdT-, beta F1+ but exhibits no detectable WT31 positivity. These cells correspond to the CD1+, mCD3+ thymocytes and are probably the targets of thymic selection. The cells of the TCR-gamma delta lineage, detected by mAb TCR-delta-1 and delta TCS1, are rare (0.02 to 0.5%) among thymocytes from gestational wk 10 1/2 onward through the whole span of thymic development, but these cells include a proportion (18 to 59%) of cells expressing CD1 Ag, suggesting that these TCR-gamma delta cells differentiate in the thymus. Among the CD1+, TCR-gamma delta + thymocytes, no TdT positivity can be detected.

Adolescent↗
PubMed1989

Neoepitopes expressed by immune complexes.

The impact of antibodies or other reagents selectively reacting with neoepitopes expressed by immune complexes (IC) upon the detection and isolation of IC is reviewed. Immunoglobulin, C1q and C3 are the three components which have been most utilised for the non-specific detection of IC. Particularly C3 of these three proteins is known to express neoepitopes which arise after enzymatic cleavage of the native C3 molecule. There are several monoclonal antibodies (MoAbs) which recognise these neoepitopes and their use renders IC assays and isolation both easier and less prone to spurious interactions and interference. Furthermore these MoAbs recognise neoepitopes arising at different stages of C3 degradation which may allow analysis of the human in vivo metabolism and processing of C3 bound to IC.

Antibodies, Monoclonal↗
PubMed1988

Leukaemia and lymphoma treatment with autologous bone marrow transplantation: preclinical studies.

Following the limited success of T-cell depletion in patients undergoing allogeneic bone marrow transplantation (BMT), recent interest is focused on autologous BMT. The selection of sensitive methods for detecting residual lymphoid malignancy, the choice of very efficient complement-fixing lytic monoclonal antibodies against residual disease, and the "tailoring" of these antibodies (or their cocktails) to individual patients lead to a very high remission rate in acute lymphoid leukaemia (ALL) of bad prognosis and second remission. The future of this extension of chemotherapy toward BMT seems to be promising, but controlled trials are required to show that the purging of bone marrow contributes to this good result. Very efficient antibodies for elimination of B lymphoma cells are also available.

Antibodies, Monoclonal↗
PubMed1987

Oral allergy syndrome (OAS): symptoms of IgE-mediated hypersensitivity to foods.

Eighty highly atopic patients were selected for study because they had either atopic eczema (fifty cases) or atopic reactivity to foods, as judged by a positive skin-prick test (thirty cases). In all, sixty-five out of eighty subjects (81%) described symptoms of some kind provoked by foods, but correspondingly positive skin tests were found in only half of these, thirty-three out of eighty (41%). The symptoms experienced by thirty-one of the thirty-three patients with positive skin tests were immediate in onset (within 1 hr) and were at first confined to the upper gastrointestinal tract, the most frequent symptoms being oral irritation and throat tightness. In a proportion of these patients, further symptoms such as urticaria, asthma or anaphylaxis developed following the initial oral symptoms, which suggested the term 'oral allergy syndrome'. In the absence of the oral allergy, symptoms such as asthma, urticaria, migraine or eczema starting later than 1 hr after food were seldom associated with positive skin tests. In the oral allergy syndrome, the characteristic symptoms (strong association with positive skin tests and RAST, time of onset and sites at which symptoms are expressed) suggest a causative relationship between exposure to food antigens and specific IgE-induced release of mediators. In cases of food intolerance that lack a characteristic symptom pattern and a positive skin test or radio-allergo-sorbent test, it seems appropriate to consider non-IgE-mediated causes.

Adolescent↗
PubMed1987

Hodgkin's disease-derived cell lines--conflicting clues for the origin of Hodgkin's disease?

The origin of Hodgkin (H) and Reed-Sternberg (RS) cells remains a highly controversial issue. Studies on noncultured, freshly disaggregated biopsy material or of histological sections have not definitely established the cell lineage of HD cells, although evidence has been gathered that has allowed interpretation to favor one or the other hematopoietic cell type. In recent years a number of cell lines have been established from patients with Hodgkin's disease (HD) which are claimed to represent in vitro counterparts of H-RS cells. The phenotypic and functional properties of 7 HD-derived cell lines are reviewed here. The cell lines are not identical; they show many common features, but also a number of important differences in their phenotypes as well as in their in vitro behavior. The cell lines differ with some having characteristics of T cells, others of B cells, and yet others of the monocyte/macrophage cell lineage. This heterogeneity of H-RS established cell lines could be explained in a variety of ways: (a) the heterogeneity of HD itself might result from a disease process which leads to fusion of different cell types resulting in different phenotypic forms of H-RS cells depending on the cells involved; (b) the different cell types might reflect differences in the malignant cells present in the separate subtypes of HD; (c) the difficulty in successfully establishing H-RS cell lines might mean that unrepresentative cell types adapt to in vitro conditions. Rather than resolve the origin of H-RS cells, the established HD-derived cell lines have been consistent with the heterogeneity described in histochemical, immunohistological, and immunocytochemical studies.

Adult↗
PubMed1986

Sub-class of IgG in allergic disease. I. IgG sub-class antibodies in immediate and non-immediate food allergy.

Previous studies have suggested that, apart from IgE-mediated reactions, some of the symptoms of food allergy may be caused by IgG antibodies to food proteins. This study was carried out to see if there were any distinctive features of the IgG sub-class antibody response to dietary antigens which occurs in food allergic patients. IgG sub-class antibodies were measured using a quantitative enzyme-linked immuno-sorbent assay (ELISA) to wheat gliadin, ovalbumin and bovine casein in twenty patients who had coeliac disease and in twenty-eight egg allergic patients. These were compared with twenty-one atopic dermatitis patients who did not have food allergy and twenty-six healthy control subjects. Coeliac disease patients tended to have raised IgG antibody levels (especially IgG1) to all three antigens but these overlapped considerably with that seen in egg allergic and atopic dermatitis patients. Coeliacs who avoided gluten had anti-gliadin antibody levels which did not differ from those seen in healthy subjects but nevertheless had raised anti-ovalbumin and casein-specific antibodies. The IgG antibody was largely restricted to IgG1 and IgG4 sub-class although the relative amount of each varied with the antigen. Although gliadin-specific antibodies were mainly IgG1, ovalbumin-specific antibodies were mainly IgG4. The increased antibody levels to all three antigens in coeliacs were caused by a raised IgG1 response, IgG4 antibodies were usually normal. Egg allergic patients also had raised IgG1 but not IgG4 antibodies to ovalbumin. These data show that the response to different dietary antigens can vary with the antigen. The fact that IgG1 and not IgG4 antibodies were raised to all three antigens in patients with coeliac disease suggests that they are a secondary consequence of the disease, perhaps reflecting increased transport of antigens across a damaged gut mucosa rather than a specific immunopathological reaction. However, the observation that antibodies to gliadin, and not ovalbumin or casein, fell following gluten avoidance shows that the response to gliadin, at least, is dependent upon continued exposure to antigen.

Adult↗
PubMed1986

Human immune responses in vivo to protein (KLH) and polysaccharide (DNP-Ficoll) neoantigens: normal subjects compared with bone marrow transplant patients on cyclosporine.

Thymus-independent (TI) and thymus-dependent (TD) primary immune responses were measured in 67 controls and 13 bone marrow transplant (BMT) recipients treated with cyclosporine (CSP) by immunizing with a synthetic antigen (DNP-Ficoll) and keyhole limpet haemocyanin (KLH). DNP-Ficoll induced similar TI antibody responses in controls and BMT recipients except that antibody levels declined much more rapidly in BMT recipients. The IgM and IgG antibodies induced by DNP-Ficoll only recognized the DNP epitope and not the Ficoll carrier. Both IgM and IgG classes of antibody showed similar TI behaviour upon immunization and re-immunization. The antibodies to DNP-Ficoll were overwhelmingly of the IgG1 subclass. The TD response to KLH evoked both delayed hypersensitivity (DH) and antibody production. DH developed at the site of immunization in 68% of controls and in 88% upon subsequent challenge with KLH. None of the BMT recipients on CSP developed DH. KLH antibody arose in 88% of controls but in only one BMT recipient on CSP. Eight BMT recipients were re-immunized with KLH 2-6 weeks after stopping CSP and only one made primary DH and antibody responses, arguing that CSP inhibited priming as well as any detectable response to KLH. The immunization procedure described has proved a sensitive and comprehensive method of quantitating human immune responses in vivo and is readily adaptable for in vitro studies.

Adolescent↗
PubMed1986

An efficient one-step method for isolating immune complexes from whole serum using a monoclonal anti-C3g affinity immunosorbent.

A simple and efficient method of extracting complement-fixing immune complexes (IC) from whole serum and recovering them has been developed. 125I-labelled, in vitro prepared IC in whole serum were incubated with Sepharose 4B covalently linked to monoclonal anti-C3g or anti-C1q and the binding and recovery of IC was monitored by radioactivity. The anti-C3g immunosorbent bound 45% and 76% of HAGG and BSA-anti-BSA IC respectively, all of which were recovered by elution with 4M MgCl2. The anti-C1q immunosorbent only bound 14% and 12% of the same IC and only 64% were recovered by eluting with 4M MgCl2. The IC extracted by the anti-C3g immunosorbent included those capable of extraction by the anti-C1q. The anti-C3g monoclonal recognizes not only the iC3b fragment of C3 and will therefore bind IC with affinity for bovine conglutinin but also subsequent degradation products containing the C3g antigen. Its wide range of reactivity for IC plus its excellent recovery properties make it the immunosorbent of choice for isolating complement-fixing IC.

Antibodies, Monoclonal↗
PubMed1985

A new method of iodinating ovalbumin, a protein which lacks accessible tyrosine groups, by conjugation to a highly fluorescent coumarin active ester, CASE.

A simple and efficient method is described to overcome the difficulty in radiolabelling ovalbumin and is applicable to any protein. Coumarin-3-acetic acid-N-OH-succinimidyl ester (CASE) binds directly to ovalbumin in aqueous solution to form covalent bonds with free amino groups. The attached CASE residues can then be radiolabelled by the chloramine-T method. This offers an inexpensive alternative to the Bolton and Hunter reagent with the advantage that CASE is fluorescent. This property, apart from direct use as a fluorescent tag, allows one to monitor the conjugate before radiolabelling. Below a conjugation ratio of 9:1, CASE-ovalbumin retained full antigenic identity with ovalbumin.

Animals↗
PubMed1985

Impaired human antibody response to the thymus-independent antigen, DNP-Ficoll, after splenectomy. Implications for post-splenectomy infections.

A synthetic thymus-independent (TI) antigen, dinitrophenyl-'Ficoll', was used to immunise controls, untreated patients with Hodgkin's disease (HD), and patients who had had splenectomy (most for staging in HD). The antibody response to DNP-ficoll was much lower in splenectomised patients than in the other groups and the antibody titres 7, 14, and 21 days after immunisation of splenectomised patients were approximately a tenth of the titres in the other groups. In contrast patients who had been primed with DNP-ficoll before splenectomy responded normally to re-immunisation 6-28 months after splenectomy. These results suggest that the antibody response upon first exposure to certain TI antigens occurs mainly in the spleen. Antibody responses are not generally impaired in splenectomised patients immunised with pneumococcal or other bacterial polysaccharides, probably because natural exposure and priming by these TI antigens before splenectomy are widespread. However, such patients must be vulnerable to overwhelming infection by encapsulated bacteria not met before splenectomy.

Antibody Formation↗