Search PubMed⌕ Search

Biomedical subjects

D Catty

Publications and source records attributed to D Catty.

At least 19 recordsLinked to original sources
PubMed1991

Genetic analysis of superoxide dismutase, the 23 kilodalton antigen of Mycobacterium tuberculosis.

The gene encoding a 23 kilodalton protein antigen has been cloned from Mycobacterium tuberculosis by screening of a recombinant DNA library with monoclonal antibodies. The product of the gene has been identified as the superoxide dismutase (SOD) of M. tuberculosis on the basis of sequence comparison and by expression of the recombinant protein in a functionally active form. The derived amino acid sequence of M. tuberculosis SOD reveals a close similarity to manganese-containing SODs from other organisms, in spite of the fact that previous studies using the purified enzyme have identified iron as the preferred metal ion ligand. SOD is present in the extracellular fluid of logarithmic-phase cultures of M. tuberculosis, but the structural gene is not preceded by a signal peptide sequence. Insertion of the M. tuberculosis SOD gene into a novel shuttle vector demonstrated the mycobacteria but is ineffective in Escherichia coli.

Amino Acid Sequence↗
PubMed1990

Characterization of a Mycobacterium tuberculosis insertion sequence belonging to the IS3 family.

A repetitive element (IS986), previously isolated from Mycobacterium tuberculosis and shown to detect multiple restriction fragment-length polymorphisms (RFLPs), has been sequenced. It consists of a potential insertion sequence of 1358bp, with 30-bp inverted repeat ends. IS986 has four potentially significant open reading frames (ORFs): ORFa1, ORFa2 and ORFb on one strand and ORFc on the complementary strand. The sequences of the potential translated products identify IS986 as a member of the IS3 family, with an apparent frameshift between ORFa1 and ORFa2. IS986 has potential as a highly specific probe for detection and typing of M. tuberculosis, as well as for transposon mutagenesis of mycobacteria. The sequence of IS986 is virtually identical to that of another recently described element, IS6110 (Thierry et al., 1990).

Amino Acid Sequence↗
PubMed1990

Insertion element IS986 from Mycobacterium tuberculosis: a useful tool for diagnosis and epidemiology of tuberculosis.

IS986 of Mycobacterium tuberculosis belongs to the IS3-like family of insertion sequences, and it has previously been shown to be present in multiple copies in the chromosome of M. tuberculosis. In this study we investigated the value of a IS986-based DNA probe in the diagnosis and epidemiology of tuberculosis. IS986 was found only in species belonging to the M. tuberculosis complex. Independent isolates of M. tuberculosis complex strains showed a very high degree of polymorphism of restriction fragments which contained IS986 DNA. In contrast, Mycobacterium bovis BCG vaccine strains as well as clinical isolates of M. bovis BCG contained one copy of IS986, which was present at the same location in the chromosome. Different M. tuberculosis isolates from a recent M. tuberculosis outbreak showed an identical banding pattern. We concluded that IS986 is an extremely suitable tool for the diagnosis and epidemiology of tuberculosis.

Animals↗
PubMed1990

Development of a species-specific ELISA for Brazilian pit-viper venoms.

Antigenic cross-reactivity between venoms of the genus Bothrops has been shown to be an extensive problem. However, some venom components are species-specific. In this study we have produced species-specific antivenoms against some members of the genus Bothrops. Monospecific rabbit antivenoms (IgG) were absorbed on venom affinity adsorbents. The species-specificity was tested by ELISA assays and immunoblots. The results of both assays showed complete species-specificity in some cases and highly increased species-specificity in others. These reagents can be used to determine the envenomating species in snake bite patients as an aid to improved serotherapy.

Antivenins↗
PubMed1987

The idiotypy of auto anti-allotype antibody induced in immunoglobulin allotype suppressed rabbits.

Rabbit anti-rabbit idiotype antibody was raised to both clonally heterogeneous and restricted auto anti-b6 antibodies induced in b6 allotype-suppressed (b6)/(b6) homozygous and b4/(b6) heterozygous rabbits. In every case the anti-idiotypic antibodies were specific only for the inducing antibody as shown by direct binding solid-phase RIA. Anti-idiotypes directed to the same antibody preparation had a similar but not identical specificity. It was demonstrated by IEF that the same idiotype specificity (spectrotype) was present throughout the anti-b6 response in individual rabbits.

Animals↗
PubMed1987

Escape from b locus allotype suppression in the rabbit is mediated by IgM molecules bearing an allotope-restricted variant of kappa light chain.

Rabbits homozygous for b6 at the kappa light chain b locus were suppressed for the expression of the b6 allotype and then induced to produce auto anti-b6 antibody. Rabbits which subsequently escaped suppression produced auto antibody with restricted allotype specificity. Escape from allotype suppression was mediated by IgM bearing a kappa chain variant with a restricted number of b6 allotopes and having a diminished interaction with auto anti-b6 antibodies from the same and other rabbits escaping b6 suppression. This suggested that there were allelic variants or subpopulations of the b6 light chain which were under independent regulation of expression, clearly influenced by the specificity of auto anti-allotype antibody. Since escape from suppression was mediated by IgM it is proposed that a normal pathway of B cell differentiation occurs during recovery from suppression.

Animals↗
PubMed1987

Antibody isotypes in human schistosomiasis mansoni.

Schistosoma mansoni-infected subjects from the Gezira Irrigated Area of Sudan were studied for serum immunoglobulin levels, and specific antibody titres to larval, adult and egg stage antigens, by class and IgG subclass. The 276 subjects were adult chronic cases (frequently exposed male canal cleaners), primary school children, and hospital-referred cases with acute symptoms including hepatosplenomegaly. Chronic untreated cases were compared with a similar group of canal cleaners 3 months after successful chemotherapy with Praziquantel administered at the start of the non-transmission season. All cases, except those previously treated, were egg positive at the time of blood sampling. Data from infected and treated cases were compared with measurements of serum immunoglobulin in a panel of European blood donors. The major findings are as follows: There is a consistently elevated total serum IgG concentration in infected groups which is accounted for mainly by an increased IgG1 subclass (greatest in chronic cases) and by a remarkable 10- to 11-fold increase in IgG4 in the untreated chronically infected group and in the schoolchildren. All infected groups showed high IgG antibody responses to all life cycle stage antigens, and IgM titres were high to adult and egg antigens in untreated canal cleaners. Major differences were evident in the distribution of IgG subclass antibodies between the infected groups: the response to larval and adult antigens is poor or absent in IgG1, IgG2 and IgG3 in untreated chronic infections but is high in IgG4, whereas in acute cases with hepatosplenomegaly and in school-children IgG1, IgG2 and IgG3 antibodies to larval antigens are in high titre but IgG4 and IgM responses to larvae are low or absent, the response in these isotypes being restricted in these cases to adult and egg antigens. Comparing the treated and untreated canal cleaners, although these are separate groups, the data suggest that Praziquantel reduces total serum IgA and IgM levels but has little effect on the raised IgG component except for the IgG4 subclass. The treated chronic cases show a reversal in the ratio of IgG1, IgG2 and IgG3 to IgG4 antibodies to larval and adult antigens compared with the untreated chronic group-the IgG4 response being low by 3 months after treatment and the IgG1, IgG2 and IgG3 being high. These data are discussed in relation to the possible importance of antibody isotype selection in determining host susceptibility to infection, with reference to age, exposure and treatment of the host.

Adolescent↗
PubMed1987

Antibody isotypes of immune complexes in schistosomiasis mansoni in Sudan.

From a panel of monoclonal antibodies to Schistosoma mansoni, one that is specific to a shared cercarial and schistosomular antigen, and does not react with other major parasite species including Fasciola hepatica, was selected for use as an antigen-capture layer in a sandwich ELISA for detection of specific circulating immune complexes in the blood of S. mansoni-infected subjects from Sudan. The test, which identifies immune complexes of only a single antibody-bound antigen, is developed using human Ig class- and IgG subclass-specific enzyme (HRP)-antibody conjugates. European blood donor sera and those with rheumatoid factor and/or anti-nuclear antibody are negative in this test. The prevalence and distribution of the different antibody isotypes in antigen-specific complexes was determined in 276 subjects of four infection groups; primary school children, adult irrigation canal cleaners with chronic infections, an equivalent group of Praziquantel cured canal cleaners, and hospital-referred cases with severe hepatosplenic symptoms. The isotype profiles of antibodies in the specific complexes were compared with those in the total serum complexes prepared by polyethylene glycol precipitation. In chronic infections and in children there is a high prevalence of IgG and IgM specific complexes, the IgG being predominantly IgG1, with little or no IgG3 and IgG4. Treated chronic infections show reduced specific complexes in all classes of antibody. Compared with chronic and children's infections, a large proportion of the patients with severe infections have in addition to high IgM, high levels of IgG2, IgG3 and IgG4 specific complexes, a fact which suggests a causal relationship between antibody production in one or more of these subclasses to the circulating antigen and symptoms of hepatosplenic disease. Although all subjects have significant amounts of total serum complexes with IgG, untreated chronic infections have much higher concentrations than other infected groups. This group also has the highest levels and prevalence of IgM and IgE complexes. In treated chronic cases IgG and IgM total complexes are greatly reduced. The significant finding in patients with severe symptoms is the relatively high IgA immune complex level compared with other groups. Taken overall the results suggest that screening of populations in endemic regions for serum immune complexes by specific and non-specific means could offer valuable data on the significance of antibody responses to circulating antigens in different isotypes in relation to pathogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1985

Presence of kappa 2 light chain in normal rabbits and as induced auto anti-allotype antibody in kappa 1 light chain suppressed subjects.

Using an antiserum raised in b(bas)/b(bas)-suppressed rabbits to kappa 2 light chain we have shown that the kappa 2 light chain is an isotype of kappa 1, present in the majority of, if not all, rabbits. It probably exists in at least 2 allelic forms. It is capable of producing a functional antibody molecule (auto anti-b6) and compensates for the absence of kappa 1 light chain in homozygous b6-suppressed rabbits.

Animals↗
PubMed1985

Improved methodology for the production of monoclonal antibodies against parasites.

A modification of the standard fusion methodology is described which results in greatly increased yields of monoclonal antibodies against certain organ-specific parasites. Several fusions were carried out using mice infected with Schistosoma mansoni or Nematospiroides dubius, using B lymphocytes harvested from either the spleen or the mesenteric lymph nodes. Results indicated a greatly improved yield of positive clones using the lymph nodes as a source of B cells for fusion. A 7-fold increase in the number of positive clones was seen with N. dubius injections, while S. mansoni fusions showed a 2-fold increase.

Animals↗
PubMed1985

Demonstration of the clonality and specificity of an auto-antibody response to a suppressed immunoglobulin allotype of the rabbit kappa chain b locus.

A regulatory idiotypic network is proposed to control allotype expression in normal rabbits. We have used suppression of the kappa chain b6 allotype in an attempt to restrict the number of regulatory idiotypes involved in an induced auto anti-allotype response. These auto anti-b6 antibodies were examined by an agarose imprint immuno-fixation IEF technique using iodinated allotype-bearing IgG. All totally b6-suppressed rabbits produced a clonally complex response which was generally spectrotypically unique - thus contradicting previous claims of a dominant common idiotypic pattern. The compensating light chains thus have available as many regulatory V genes as does the kappa 1 light chain. However, the b6/b6 homozygotes breaking b6 suppression produce an auto anti-b6 antibody which does not interact with their "escaping" molecules and which is clonally restricted. We propose a regulatory mechanism limiting the V genes utilised to produce the autoantibody, the latter then allowing only molecules bearing non-interactive allotopes to "escape" suppression.

Animals↗
PubMed1985

A secondary immune deficiency in the Fatty/Orl-op rat.

The response of T and B lymphocytes to the mitogens PHA and LPS was studied in the Fatty/Orl-op rat. Whereas T and B cells from op/op spleen showed no lack of responsiveness compared with that of normal (op/+) littermate rats, the response of thymic cells to the T cell mitogen was lower in op/op rats over 12 days of age compared with normal rats of the same age. Osteopetrotic rats of 10 days and younger did not show this T cell deficiency. The responsiveness of T cells from op/op lymph nodes to PHA was less than that of normal rats at 12 days and older. Thus, though splenic T and B cell populations were well maintained in the adult op/op rat despite the severe depletion of marrow cells in this mutant, the thymus and lymph node T cell populations were qualitatively or quantitatively deficient. Since osteopetrotic obliteration of the marrow cavities precedes the appearance of the immune deficiency we suggest that the immune deficiency may be caused by a failure of T cell supply to the thymus and lymph nodes.

Animals↗
PubMed1985

Quantitative and spectrotypic analysis of paternal IgG2a expression in normal and allotype-suppressed mice.

The synthesis and clonal diversity of IgG2a molecules bearing the paternally inherited immunoglobulin allotype have been examined in the offspring of matings between BALB/c mothers (Igh-1a) and SJL or C57BL/10 males (both Igh-1b) using a sensitive quantitative single radial immunodiffusion in gel assay and isoelectric focusing with autoradiography. In normal litters, the first detectable paternally-marked IgG2a is extensively polyclonal in both F1 crosses (i.e. diversity precedes expression); however, there is a delay of 2-3 weeks in the first appearance of the clonally diverse set of molecules when these are coded by the SJL genome, compared with the C57BL/10. Delayed maturation of allelically-excluded Igh-1b-expressing B cells in the (BALB/c X SJL)F1 may explain the unique susceptibility of these offspring to chronic allotype suppression when exposed to maternal anti-Igh-1b antibodies in early life. We find that, although such suppressed mice may begin life with a (delayed) synthesis of polyclonal IgG2a of paternal allele (Igh-1b), the condition of chronic suppression later imposed in the majority of mice is associated with spectrotype (clonal) simplicity.

Animals↗
PubMed1979

Surface Ig on rabbit lymphocytes. Rabbit B and T cells are distinct populations.

Rabbit peripheral blood lymphocytes (PBL) were analyzed by immunofluorescence using anti-T cell conjugates and anti-Fab, anti-a1 allotype, anti-IgM and anti-IgA conjugates. In addition, T cells were demonstrated by rosetting with papain-treated homologous erythrocytes. Control experiments, using acid treatment and incubation at 37 degrees C for 18 h after or without pronase treatment, revealed the endogenous origin of all surface determinants tested. A good correlation was found between results obtained with the two anti-T cell conjugates used and the T rosette test on PBL and on lymphoid cells isolated from various organs. In lymphocytes isolated from peripheral blood and from various lymphoid organs, the percentages of T and B cells were respectively 45 and 38 for PBL, 10 and 46 for bone marrow, 27 and 31 for appendix, 40 and 45 for spleen, 42 and 46 for Peyer's patches, 96 and 0.3 for thymus and 70 and 16 for peripheral lymph nodes. The percentage of "null" cells in lymphocyte populations derived from bone marrow and appendix is rather high. The final percentages of T and B cells in rabbit PBL depend to a significant extent on the method of isolation, especially isolation by Ficoll-Hypaque centrifugation results in a depletion of T cells. Moreover, a rather impure lymphoid cell suspension is obtained. In double incubation experiments, T cells (as defined by T cell antigen(s) or rosette formation) and B cells (Fab-bearing cells) were entirely different subpopulations. Allotypes of the a locus could not be detected on the surface of T cells. The results are discussed with respect to genetic coding of antigen receptors on B and T cells.

Animals↗
PubMed1979

Multiple Ig classes on rabbit B lymphocytes.

Rabbit PBL were studied regarding the presence of different classes of s-Ig, under experimental conditions, ensuring the endogeneous origin of these proteins. About 40% of the lymphocytes are B cells (Fab positive and a1 positive in a1 homozygous rabbits). IgG positive lymphocytes could be found, but only using and anti dll conjugate (allotype located on the Fd gamma region of IgG). Anti Fc gamma conjugates were negative. Most of the B cells are IgM positive, most of these IgM cells however were also positive for either IgG or IgA. Np lymphocytes were found bearing both IgG and IgA. Careful analysis of the percentages of various isotypes found on B cells suggests that some "IgD" positive lymphocytes could be present. Results are discussed in relation to B cell differentiation.

Animals↗