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Biomedical subjects

L Gaur

Publications and source records attributed to L Gaur.

12 recordsLinked to original sources
PubMed2005

Chimerism analysis by sex determining region Y (SRY) and major histocompatibility complex markers in non-human primates using quantitative real-time polymerase chain reaction.

The ability to discriminate and further quantify the proportion of donor and host cells is essential in hematopoietic stem cell transplant protocols. In human sex-mismatched transplants, this can be easily accomplished by the use of commercially available fluorescent in situ hybridization (FISH) probes. In many animal models, including non-human primates, this methodology is not possible due to the lack of commercially available FISH probes. In animal models, donor cell detection could be accomplished if there is a known species-specific sex determining region Y (SRY) (male) or other unique DNA sequence using either semiquantitative or quantitative real-time polymerase chain reaction (PCR). The use of real-time quantitative PCR has the obvious advantage of providing detailed enumeration of the percentage of donor cells present. We report the development of extremely sensitive primer and probe combinations for male (SRY) and major histocompatibility complex (MHC)-DQA sequences in the macaque and baboon non-human primate models. This assay has a sensitivity of a five-log range and can detect less than four target cells in the presence of 10(5) background cells (approximately 0.001%) and fetal DNA obtained from maternal serum from Macaca nemestrina. The SRY (male) primer and probe combination has similar sensitivity in Macaca fasicularis, Macaca mulatta, and Papio cynocephalus anubis.

Animals↗
PubMed2001

Complexity of human immune response profiles for CD4+ T cell epitopes from the diabetes autoantigen GAD65.

Complex protein antigens contain multiple potential T cell recognition epitopes, which are generated through a processing pathway involving partial antigen degradation via proteases, binding to MHC molecules, and display on the APC surface, followed by recognition via the T cell receptor. We have investigated recognition of the GAD65 protein, one of the well-characterized autoantigens in type I diabetes, among individuals carrying the HLA-DR4 haplotypes characteristic of susceptibility to IDDM. Using sets of 20-mer peptides spanning the GAD65 molecule, multiple immunostimulatory epitopes were identified, with diverse class II DR molecules functioning as the restriction element. The majority of T cell responses were restricted by DRB1 molecules; however, DRB4 restricted responses were also observed. Antigen-specific T cell clones and lines were derived from peripheral blood samples of pre-diabetic and IDDM patients and T cell recognition and response were measured. Highly variable proliferative and cytokine release profiles were observed, even among T cells specific for a single GAD65 epitope.

Amino Acid Sequence↗
PubMed1998

Biased T-cell antigen receptor repertoire in Lyme arthritis.

A common concern with many autoimmune diseases of unknown etiology is the extent to which tissue T-lymphocyte infiltrates, versus a nonspecific infiltrate, reflect a response to the causative agent. Lyme arthritis can histologically resemble rheumatoid synovitis, particularly the prominent infiltration by T lymphocytes. This has raised speculation about whether Lyme synovitis represents an ongoing response to the causative spirochete, Borrelia burgdorferi, or rather a self-perpetuating autoimmune reaction. In an effort to answer this question, the present study examined the repertoire of infiltrating T cells in synovial fluid from nine Lyme arthritis patients, before and after stimulation with B. burgdorferi. Using a highly sensitive and consistent quantitative PCR technique, a comparison of the T-cell antigen receptor (TCR) beta-chain variable (Vbeta) repertoires of the peripheral blood and synovial fluid showed a statistically significant increase in expression of Vbeta2 and Vbeta6 in the latter. This is remarkably similar to our previous findings in studies of rheumatoid arthritis and to other reports on psoriatic skin lesions. However, stimulation of synovial fluid T cells with B. burgdorferi provoked active proliferation but not a statistically significant increase in expression of any TCR Vbeta, including Vbeta2 and Vbeta6. Collectively, the findings suggest that the skewing of the TCR repertoire of fresh synovial fluid in Lyme arthritis may represent more a synovium-tropic or nonspecific inflammatory response, similar to that occurring in rheumatoid arthritis or psoriasis, rather than a specific Borrelia reaction.

Adolescent↗
PubMed1998

HLA-DRB1 typing in rheumatoid arthritis: predicting response to specific treatments.

OBJECTIVE: To determine the predictive value of shared epitope alleles for response to treatment in patients with rheumatoid arthritis. METHODS: Patients from our previously published triple DMARD study were tested for the presence of shared epitope alleles (DRB1 *0401, 0404/0408, 0405, 0101, 1001, and 1402). Patients who were shared epitope positive were then compared with those who were negative to see if there was a differential effect on therapeutic response. RESULTS: Shared epitope positive patients were much more likely to achieve a 50% response if treated with methotrexate-sulphasalazine-hydroxychloroquine compared with methotrexate alone (94% responders versus 32%, p < 0.0001). In contrast shared epitope negative patients did equally well regardless of treatment (88% responders for methotrexate-sulphasalazine-hydroxychloroquine versus 83% for methotrexate). Additionally, a trend toward an inverse relation of the gene dose was seen for response to methotrexate treatment (p = 0.05). CONCLUSIONS: These data suggest that determining shared epitope status may provide clinical information useful in selecting among treatment options.

Adult↗
PubMed1998

Analysis of platelet glycoprotein Ia (alpha2 integrin) allele frequencies in three North American populations reveals genetic association between nucleotide 807C/T and amino acid 505 Glu/Lys (HPA-5) dimorphisms.

Glycoprotein Ia (alpha2 integrin) is a subunit of the heterodimeric membrane complex (GPIa/IIa) that mediates platelet adhesion to collagen. Several nucleotide sequence variations of GPIa have been described. A nucleotide 1648 G/A dimorphism that leads to a Glu/Lys substitution at amino acid 505 is responsible for the human platelet antigen system, HPA-5. Recently, two other linked GPIa nucleotide dimorphisms involving codons Phe224 and Thr246 were identified: a C/T substitution at nucleotide 807 and a G/A substitution at nucleotide 873(1). Using restriction enzyme digestion of amplified GPIa genomic DNA fragments (PCR-RFLP) to distinguish genotypes, we have determined the allele frequencies of the GPIa 807C/T and Glu/Lys505 dimorphisms in three North American populations, and a panel of non-human primates. Our results indicate a genetic relationship between the 807C/T and Glu/Lys505 dimorphisms that leads to an evolutionary model of GPIa isoforms.

Alleles↗
PubMed1997

Prolonged allogeneic and xenogeneic microchimerism in unmatched primates without immunosuppression by intrathymic implantation of CD34+ donor marrow cells.

Engraftment of stem cell-enriched donor marrow implanted in the thymus of a foreign host might facilitate acceptance of donor-specific organ or tissue grafts. To test this hypothesis, allogeneic and xenogeneic CD34+ marrow cells from unrelated adult male baboons and humans were injected intrathymically in eight infant female baboons, both with and without standard cyclosporine-based immunosuppression. In allogeneic experiments, male (donor) cells, of both T- and B-cell lineages, were detected by PCR in the peripheral blood of all six recipients and persisted for at least 15 months in 2/4 recipients studied longtutudinally. Donor-derived skin grafts survived twice as long as third party grafts in unimmunosuppressed recipients. In xenogeneic protocols, human male (donor) cells were demonstrable for 7 and 15 months, respectively, in two baboon recipients with evidence that implanted human CD34+ cells had produced lymphoid progeny. Survival of donor-specific skin xenografts was prolonged in one of two recipients. These experiments demonstrate that the intrathymic injection of CD34+ marrow cells can result in long-lasting lymphohematopoietic microchimerism in unrelated primates even without immunosuppression and can alter donor-specific skin graft survival.

Animals↗
PubMed1987

Expression of the human B-cell surface protein CD20: alteration by phorbol 12-myristate 13-acetate.

The monoclonal antibody 1F5 recognizes human B-cell surface protein CD20 and can activate resting B cells; with this antibody we found CD20 to be a 35/37-kDa non-disulfide-linked protein. The protein has a pI of 7.5-8.0 and is phosphorylated in B-cell lines, tonsillar B cells, and peripheral blood B cells. Both CD20 surface expression and phosphorylation are increased on buoyant tonsillar B cells activated in vivo. Because phorbol 12-myristate 13-acetate (PMA) supports the activation signal initiated by monoclonal antibody 1F5, we studied the effect of PMA on CD20 expression. After brief incubation with mitogenic levels of PMA, the number of dense tonsillar B cells positive for CD20 protein transiently decreased. Paradoxically, the cells remaining positive had more surface CD20 than did control cells, and these remaining surface CD20 molecules were hyperphosphorylated. Furthermore, PMA not only induced phosphorylation of CD20 protein on Raji cells but also increased the internalization of CD20 molecules; both phosphorylation and internalization of CD20 molecules were decreased with the protein kinase C inhibitor palmitoyl carnitine. Conditions that increase CD20 phosphorylation are shown also to increase surface mobility of the molecule, suggesting that CD20 protein internalization may be a critical early event for B-cell entry into the G1 phase of the cell cycle.

Antibodies, Monoclonal↗
PubMedDate not supplied

Dynamics of contraceptive practice amongst urban Indian women.

BACKGROUND: Most studies on knowledge, attitude and practice regarding contraceptives have been conducted in rural areas and urban slums. In this study, a mixed urban population was surveyed. SUBJECTS: Two thousand parous women from different social and educational backgrounds residing in the metropolis of Mumbai (Bombay), Maharashtra were included in the study. RESULTS: Fifty per cent of illiterates, semi-literates and highschool educated, and 80% of college-educated couples said that they had no gender preferences for their children, but actual practice belied this. Regardless of the level of education, 25%, 75% and 95% of all couples were sexually active by 6 weeks, 3 months and 6 months after childbirth. Awareness regarding the availability of various contraceptives increased with education; 20% of all graduate couples used condoms or the rhythm method immediately after marriage. After the birth of their first child, 80% of educated couples used spacing methods whereas even after the birth of their third child more than 50% of the uneducated did not. The major complaint of the intrauterine device users was menorrhagia and abdominal pain, while that of pill users was nausea, giddiness and headache. Spacing methods were popular among the educated, and terminal ones among the uneducated. Steroidal contraceptive pills were not popular with any group, regardless of the level of education. CONCLUSION: Education was the main variable in the decisions regarding the family size, spacing interval, contraceptive awareness, its use immediately after marriage and during the postpartum period.

Contraception↗