Biomedical subjects

J Farrant

Publications and source records attributed to J Farrant.

At least 19 recordsLinked to original sources

PubMed1992

Effect of 12,13-phorbol dibutyrate and ionomycin on defective B cells in common variable immunodeficiency.

Secretion of IgM and IgG in vitro by B cells from patients with common variable immunodeficiency (CVI) has been used to classify the disease into three groups. On stimulation with anti-IgM and IL-2, group A patients' cells fail to secrete IgM or IgG, group B patients' cells secrete no IgG and significantly lower levels of IgM than normal cells, and group C patients' cells produce normal levels of both isotypes. Direct activation of protein kinase C using 12,13-phorbol dibutyrate and ionomycin followed by IL-2 or IL-4 has been reported to induce immunoglobulin secretion by normal human B cells. We therefore attempted to induce B cells from group A and group B CVI patients to secrete IgM and IgG after direct activation of protein kinase C together with IL-2 or IL-4. The data show that the failure of secretion of immunoglobulin by B cells from CVI patients could not be reversed using this approach. This finding suggests that the activation channel involving protein kinase C in B cells from CVI patients is not involved in the defect in cell differentiation.

B-Lymphocytes↗

PubMed1992

LFA-1-dependent OKT3-driven T cell clusters in common variable immunodeficiency.

The triggering of the TCR/CD3 complex by anti-CD3 (OKT3) antibody leads to the formation of T cell clusters. In cultures of T lymphocytes from most normal individuals, the peak of cluster formation occurs at 24 h, but with cells from patients with common variable immunodeficiency (CVI) it was seen earlier at 4-9 h; in addition, the clusters were larger than normal, particularly at 9 h. Cluster formation by CVI and normal cells was dependent on temperature and divalent cations, but did not require Fc receptors. Since OKT3 clustering is known to be dependent on the LFA-1/ICAM-1 adhesion system, the effect of monoclonal antibodies directed against these molecules was tested. A potent inhibitor was the antibody against the common beta chain of the integrin family (CD18), but of four MoAbs against the alpha chains (CD11), three inhibited and one stimulated T cell aggregate formation. Increased expression of LFA-1 or ICAM-1 on CVI patients' T cells could not be demonstrated. The accelerated clustering was therefore probably due to an increase in the proportion of cells carrying the activated form of LFA-1. The formation of large numbers of homotypic lymphocyte clusters might reduce the effective interaction between B and T cells, thus contributing to the depression of immunoglobulin synthesis observed in this disease.

Adolescent↗

PubMed1991

Bronchiectasis in hypogammaglobulinaemia--a computed tomography assessment.

To determine the pattern of bronchiectasis in hypogammaglobulinaemia we reviewed the CT scans of 38 hypogammaglobulinaemic patients. Twenty-two had bronchiectasis, seven had bronchial wall thickening without bronchiectasis and the remaining nine were normal. The middle lobe was the most common site of bronchiectatic involvement, followed by the lower lobes and the lingula. There were no cases of isolated upper lobe involvement. In patients who had bronchial wall thickening without bronchiectasis the middle lobe and lower lobes were again most commonly affected. It is postulated that in these hypogammaglobulinaemic patients bronchial wall thickening represents a stage of bronchial inflammation prior to the development of bronchiectasis. Patients with X-linked agammaglobulinaemia (XLA) develop bronchiectasis at a significantly earlier age than those with 'common variable' hypogammaglobulinaemia (CVH) (P = 0.02). No correlation was found between the serum levels of immunoglobulin classes at diagnosis and the subsequent development of bronchiectasis.

Adolescent↗

PubMed1991

Cytokine-independent progression of immunoglobulin production in vitro by B lymphocytes from patients with systemic lupus erythematosus.

B lymphocytes from patients with systemic lupus erythematosus (SLE) secreted high levels of immunoglobulin spontaneously when cultured in vitro. Addition of the cytokines interleukin-2, interleukin-4 and interleukin-6 either alone or in combination failed to augment spontaneous immunoglobulin synthesis. Percoll-separated low-density SLE B lymphocytes matured into immunoglobulin-secreting cells also independent of exogenous interleukins. During maturation these cells became enlarged and less dense, and began to express CD23. This was in contrast to normal B cells, which did not secrete immunoglobulin spontaneously but synthesized IgM after interleukin stimulation. These results indicate that in vitro immunoglobulin synthesis by SLE B cells is already initiated in these cells and progresses independently of further stimulatory manoeuvres.

Antigens, Differentiation, B-Lymphocyte↗

PubMed1991

Common variable immunodeficiency is associated with polymorphic markers in the human major histocompatibility complex.

Common variable immunodeficiency (CVI) is a heterogeneous condition characterized by arrest in B cell differentiation. A high frequency of null alleles of the C4 gene has been reported in patients with this disorder. We investigated the restriction fragment length polymorphisms (RFLP) of the MHC class II genes HLA-DRB, DQA, and DQB, the class III gene C4 and the tumour necrosis factor-alpha) (TNF-alpha) gene in 40 Caucasian patients. The results showed an increase in HLA-DR3 in patients (40% vs 30.5%), but, more significantly, there was a striking increase in the number of CVI patients who carried a deletion of the C4A gene (46% vs 25%). In both patients and controls there was strong allelic association between HLA-DR3 and C4A deletion, and HLA-DR3 and TNF-alpha. Our results suggest that genes present on an extended haplotype containing these three polymorphisms contribute to genetic susceptibility to CVI.

Adolescent↗

PubMed1991

Defects in proliferative responses of T cells from patients with common variable immunodeficiency on direct activation of protein kinase C.

DNA synthesis in response to mitogens has been studied in T cells from nine patients with common variable immunodeficiency (CVI) and seven normal individuals. Five out of the nine patients had cells with subnormal responses to the mitogen phytohaemagglutinin (PHA). As PHA-induced responses are largely mediated through activation of Ca(2+)-dependent protein kinase C, we studied whether the defective response was still present on direct activation of protein kinase C. This was done using combinations of concentrations of phorbol 12,13,-dibutyrate and the calcium ionophore ionomycin which induced proliferation in normal T cells. We found that in CVI patients with T cells which had normal responses to PHA, responses to phorbol ester and ionomycin were at the same level as in normal T cells. However, with this treatment, in which the linkage between the membrane receptor and protein kinase C is bypassed, the level of DNA synthesis was still depressed in the patient group whose T cells had subnormal responses to PHA. IL-2 failed to restore the DNA synthesis to normal levels when added with the phorbol ester and ionomycin to T cells from one patient in this group. These data suggest that in a group of CVI patients there are defects in T cell activation pathways at or down-stream of protein kinase C.

Cells, Cultured↗

PubMed1991

Raised serum levels of CD8, CD25 and beta 2-microglobulin in common variable immunodeficiency.

Soluble CD8, soluble CD4, soluble CD25 (IL-2 receptor), beta 2-microglobulin and the cytokine tumour necrosis factor-alpha (TNF-alpha) were measured in sera from patients with common variable immunodeficiency (CVI). Levels of soluble CD8, soluble CD25 and beta 2-microglobulin but not of soluble CD4 and TNF-alpha were raised significantly above levels in normal sera. Sera from patients with X-linked agammaglobulinaemia, who are also antibody deficient, did not show this marked elevation. The raised levels of soluble CD8, soluble CD25 and beta 2-microglobulin in CVI, correlated with the extent of the defects in the B lymphocytes assessed in vitro, as well as with the clinical severity of the disease. The selective release of these molecules into sera may indicate that abnormal cellular activation occurs in most CVI patients. It is also possible that the raised levels of these soluble molecules play a part in the immunodeficiency.

Acquired Immunodeficiency Syndrome↗

PubMed1991

Phenotypic and functional studies of human peripheral blood lymphocytes engrafted in scid mice.

CB.17 mice homozygous for the scid defect have been used as recipients of peripheral blood lymphocytes (PBL) from normal humans and from patients suffering from common variable immunodeficiency (CVI) types A and B. Following intra-peritoneal injection of PBL, such mice become chimeric with human cells, as evidenced by the presence in their serum of human immunoglobulins, which persist for a number of months. Under these conditions, B cells from CVI patients are also triggered to produce immunoglobulin. In contrast, T cells in the inocula, although they persist for 1 or 2 months in the peritoneal cavity, do not appear to function normally in antigen-specific responses and they do not recirculate in the recipient mice.

Animals↗

PubMed1991

T and B cell defects in common variable immunodeficiency.

More than 50 patients with common variable immunodeficiency have been classified into 5 groups representing different blocks in B cell function. To do this, B cells were assessed in vitro by secretion of IgM or IgG in response to anti-IgM and IL-2 or to EBV alone. Some clinical features and the patients' sex ratio correlated with this B cell classification. In vitro attempts were made to identify and overcome these blocks using physiological ligands (e.g. cytokines), and agents that induce transcription (e.g. retinoic acid). The patient group with the most severely affected B cells also contained some patients whose T cells showed depressed DNA synthesis in response to mitogens. In vitro data indicate that the abnormality may be in the T cell itself rather than in monocytes failing to provide essential cytokines (e.g. IL-6). In 3 patients, splenic B cells were able to secrete IgM more effectively than circulating B cells, but still they produced no IgG.

B-Lymphocytes↗

PubMed1991

Interleukin-2-induced DNA synthesis and immunoglobulin secretion by resting human tonsillar B cells: effects of protein kinase C activation.

Responses to interleukin-2 (IL-2) of high-density human tonsillar B lymphocytes were examined in 20 microliters hanging drop microcultures. DNA synthesis and secretion of IgM and IgG were induced by IL-2 alone. Activation of calcium-dependent protein kinase C (PKC) with phorbol 12,13-dibutyrate and ionomycin increased IL-2 driven DNA synthesis yet reduced IL-2 driven secretion of IgM and IgG. Forskolin, which increases cAMP, had no effect on the responses to IL-2. Intrinsic IL-6 played no role in IL-2-induced DNA synthesis but was partially responsible for the secretion of immunoglobulin. These data show that pre-activation of the high-density human tonsillar B lymphocyte is not a prerequisite for IL-2-driven responses. They also show an asymmetry between the growth and differentiation induced by IL-2. This is reflected by opposite modulation on activation of PKC and by the role of the autocrine factor, IL-6.

B-Lymphocytes↗

PubMed1990

Phenotypic features and proliferative activity of B cell progenitors in X-linked agammaglobulinemia.

In this study, we applied mAb and heterologous antisera in double marker combinations to investigate the phenotype and the proliferative activity of immature B lineage cells in XLA. Bone marrow (BM) samples from eight male adult patients with no circulating B lymphocytes were studied. The proportions and the phenotype of the earliest identifiable B cell progenitors, expressing nuclear terminal deoxynucleotidyl transferase (TdT), cytoplasmic CD22, and membrane CD19 and CD10 were identical to those observed in normal BM. In XLA these cells represented 1.2% to 22% of BM mononuclear cells; 5% to 42% and 1% to 45% of such cells weakly expressed CD20 and CD37, respectively, and invariably lacked CD13 and CD33. Cytoplasmic mu+ sIg- pre-B cells were seen in low numbers (0.1% to 0.3%) in four samples and were undetectable in the remaining four. Consequently, the ratio TdT+/c mu+ was greater than 100 in five out of eight samples studied in contrast to the less than 10 values seen in normal individuals. The proliferative activity of B lineage progenitor cells was studied by using Ki67 and anti-bromodeoxyuridine mAb. Although the proliferation of TdT+ cells in XLA was comparable with that seen in normal BM samples (24% to 59% of TdT+ were Ki67+ and 11% to 27% incorporated bromodeoxyuridine), this was dramatically reduced in the c mu+ cells (no c mu+, Ki67+ seen in three samples where pre-B cells were observed). Thus, the abnormalities of B cell differentiation in XLA are first seen at the c mu+ pre-B stage and suggest a maturation block in the transition between TdT+, c mu- pre-pre-B cells and c mu+ pre-B cells. The severity of this block may be variable, allowing the generation of a near normal number of pre-B cells in some patients, which nevertheless have a defective proliferative activity. Finally, our study further supports the concept that the effects of the "XLA gene" are confined within the B lineage by demonstrating that the proportions of T cells bearing TCR-alpha beta and TCR-gamma delta in XLA are similar to those seen in normal individuals.

Agammaglobulinemia↗

PubMed1990

Classification of patients with common variable immunodeficiency by B cell secretion of IgM and IgG in response to anti-IgM and interleukin-2.

We have classified patients with common variable immunodeficiency (CVI) on the basis of the ability of their B cells to respond to anti-IgM and interleukin (IL)-2 in vitro. Group A had cells unable to secrete IgM or IgG, Group B secreted IgM alone, and Group C secreted both IgM and IgG. A separate small group of patients lacked peripheral B cells. Where Ig secretion was present with anti-IgM and IL-2, EBV increased it, but where it was absent, EBV only induced IgM secretion in two out of eight Group A patients and IgG in one out of five Group B patients. These classifications are related to the sex of the patient and may represent different loci of the block in B-cell differentiation in CVI.

Antibodies, Anti-Idiotypic↗

PubMed1990

Role of interleukin-2 and interleukin-6 in the mitogen responsiveness of T cells from patients with 'common-variable' hypogammaglobulinaemia.

We have assessed the ability of interleukin-2 (IL-2) and interleukin-6 (IL-6) to augment the proliferative response of T lymphocytes from 'common-variable' hypogammaglobulinaemia (CVH) patients and from normal controls, to the mitogens phytohaemagglutinin (PHA) and OKT3. We show that with cells from the control group and from those patients whose T cells respond to PHA within the control range, both IL-2 and IL-6 will significantly augment the response to OKT3. However, in those patients with a T cell defect in which the PHA response is below the control range, neither IL-2 nor IL-6 could restore the PHA or OKT3 response to normal. Responses to IL-2 or IL-6 alone were always in or above the control range.

Agammaglobulinemia↗

PubMed1990

Cellular abnormalities in common variable immunodeficiency.

In most patients with common variable immunodeficiency (CVI) there is evidence for an intrinsic B cell defect, despite an apparently normal cell phenotype. There are at least five separate subgroups of CVI, based on B cell function. These groups may be variations in severity of a single defect, or distinct molecular defects. At least some patients may have an abnormality in the secretory process of the B cell. The existence of patients whose cells can secrete IgM and IgG in vitro and yet are hypogammaglobulinaemic in vivo implies that the architecture of lymphoid organs or the traffic of lymphoid cells may be involved in the pathogenesis of the disease. The data on T cell defects in CVI indicates that, with sensitive assays, many patients have some abnormality. In the face of a much more defined B cell defect it is not yet possible to assess the overall contribution of the T cell defects to the immune failure.

Agammaglobulinemia↗

PubMed1989

B cell function in acquired "common-variable" hypogammaglobulinemia: proliferative responses to lymphokines.

We have compared the proliferative responses of an enriched population of B lymphocytes from patients with acquired (common variable) hypogammaglobulinemia (CVH) with the responses of cells from normal individuals. The uptake of [3H]thymidine into DNA was measured on stimulation with a range of interleukins (IL-2, IL-4, and IL-6) and solid-phase anti-IgM. Flow cytometry using CD19 and surface IgM showed that the "non-T" preparations from the peripheral blood of CVH patients either contained B cells within the normal range (30-40% of the cells) or in a minority group no B cells (less than 3% of the cells). Overall, there were no significant differences between the proliferative responses of patients' cells (in the group where normal numbers of B cells were present) and normal cells with any combination of stimulus used. No IgG was produced by cells from any patient and in only one patient was IgM production observed. This suggests that the primary B lymphocyte defect in CVH is in the differentiation phase in B cell function rather than in the growth phase. However, the presence or absence of B cells suggests that different defects exist in subgroups of patients with this disease.

Agammaglobulinemia↗

PubMed1989

The role of lymphokines in common variable hypogammaglobulinemia.

Common variable (acquired) hypogammaglobulinemia (CVH) is a rare primary immunodeficiency disease of great interest as an immunological model of defects in antibody production. In this article, Gavin Spickett and John Farrant discuss evidence of abnormalities in lymphokine production and responses in the generation of the functional failure. It is not yet clear whether the B cell is intrinsically abnormal or lacks appropriate signals, but the block appears to occur in the differentiation phase of B cells, since membrane (but not secreted) IgG is made. Some T-cell defects also occur in this disease. The cause of CVH is unknown, although a viral aetiology has been suggested. Better understanding of lymphokine networks may allow the provision of specific signals to overcome the block in antibody production.

Agammaglobulinemia↗

PubMed1989

Assessment of responses of normal human B lymphocytes to different isolates of human immunodeficiency virus: role of normal donor and of cell line used to prepare viral isolate.

The effect of different HIV-1 isolates on normal human B lymphocyte function has been studied in vitro. Production of IgM and IgG was measured by ELISA using a "standard" non-T preparation of B cells depleted of macrophages and T cells (but not of low-density accessory cells, LDC). Only one (H9/CBL-4) of five different isolates induced polyclonal production of immunoglobulin. Apart from intrinsic differences between isolates, important inherent variables were shown to affect the response. One was the mix of cell types in the responding preparation of B cells. This was tested by examining the effects of HIV-1 isolates independently on the accessory function of LDC and on B cell function when the LDC were removed. Isolate H9/HTLV-IIIRf was nonstimulatory on a B cell preparation containing LDC and suppressive on LDC accessory function yet could enhance function of B cells when the LDC were depleted. Another variable was the donor of the normal B cells. The B cell response was consistent with each donor but varied greatly with different donors. Thus, no single explanation emerges for the hypergammaglobulinemia in some adult AIDS patients and for the hypogammaglobulinemia in some pediatric cases. Additionally, the cell lines used to propagate the virus particularly affected the assay of B cells depleted of LDC. Uninfected supernatants had different effects on the B cell function, and these host cell effects (perhaps by release of cytokines or other mediators) may be exacerbated in infected cell lines. Our data show the complexity of the abnormal B cell function in AIDS.

Acquired Immunodeficiency Syndrome↗

PubMed1989

Defective DNA synthesis by T cells in acquired 'common-variable' hypogammaglobulinaemia on stimulation with mitogens.

We have studied T cell defects in acquired 'common-variable' hypogammaglobulinaemia (CVH) by measuring the synthesis of DNA, RNA and protein in vitro in response to mitogens and to interleukin 2 (IL-2). We have confirmed that some patients have defective DNA synthesis in response to PHA and shown that this extends to responses to cell-derived B cell growth factor (c-BCGF) which is also mitogenic to T cells. DNA synthesis induced by IL-2 was not defective in these patients suggesting IL2-receptor induction is normal. The mitogen-related defect in DNA synthesis was not accompanied by any reduction in synthesis of RNA or of protein. Levels of the rate limiting enzyme (thymidylate synthetase EC 2.1.1.45) responsible for de novo DNA synthesis in the absence of endogenous thymidine were measured following PHA stimulation and found to be in the normal range. In the CVH patients (but not in normal individuals) the relationship between the levels of thymidylate synthetase and DNA synthesis in response to PHA approached significance, suggesting that this pathway becomes more important in CVH patients than in normal individuals perhaps because of defects in the thymidine 'salvage' pathway.

Agammaglobulinemia↗