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Biomedical subjects

I Nath

Publications and source records attributed to I Nath.

At least 73 records · Page 4Linked to original sources
PubMed1982

Rapid, radiolabeled macrophage culture method for detection of dapsone-resistant Mycobacterium leprae.

Mycobacterium leprae cells extracted from the skin biopsies of 14 bacilliferous lepromatous patients were maintained in human-murine macrophage cultures for 3 weeks in the presence of [3H]thymidine and DDS (4,4'-diaminodiphenyl sulfone). All cultures except one containing freshly extracted viable bacilli showed significant incorporation of [3H]thymidine as compared to control cultures containing heat-killed bacilli of the corresponding strain. Six susceptible strains of M. leprae obtained from untreated, freshly diagnosed patients showed significant inhibition of the uptake of the radiolabel in the presence of 3 and 10 ng of DDS per ml per culture. Eight strains of M. leprae obtained from patients clinically suspected of DDS resistance were tested in a similar manner. These strains were also concurrently inoculated in the footpads of mice given orally 10(-2), 10(-3), and 10(-4) g of DDS per 100 g of body weight for 9 months. Concordant results were obtained by both methods: five strains were found to be resistant, one was susceptible, and one was partially resistant. Strain VIII did not incorporate [3H]thymidine in the macrophage cultures and proved to be resistant in the mouse footpad. The macrophage culture system provides a sensitive, rapid screening method for the early diagnosis of DDS resistance.

Adult↗
PubMed1982

Lack of correlation between morphological index and viability as assessed by the uptake of 3H-thymidine by macrophage resident M. leprae.

Thirty strains of M. leprae derived from skin biopsies of lepromatous leprosy patients were scored for Morphological Index (MI) and concurrently maintained for 2 weeks in macrophage cultures containing 3H thymidine. Selective and significant incorporation of the radioactive label was observed in cultures containing freshly extracted M. leprae as compared to control cultures with autoclaved bacilli from the same biopsy. The percentage incorporation of 3H thymidine ranged from 103 to 1140%. Morphological Index of the bacilli from these individuals varied from zero to 8. Six cultures containing bacilli with MI of less than or equal to 1 and 3 containing bacilli with MI of zero showed significant incropration of 3H thymidine. There was no correlation between the percent of solid or beaded bacilli in the inoculum and the ability of M. leprae to incorporate 3H thymidine in the macrophage cultures.

Animals↗
PubMed1982

Radiolabelled M. leprae resident in human macrophage cultures as an in vitro indicator of effective immunity in human leprosy.

Twelve strains of human derived, freshly extracted M. leprae maintained within human macrophages showed a 2.1-13.2-fold increase in the incorporation of 3H-thymidine compared to parallel cultures containing heat-killed bacilli of the same strain. The addition of antigen stimulated lymphokines from five paucibacillary, tuberculoid leprosy patients resulted in the inhibition of the uptake of the radiolabel by 49-87%. Minimal, or no, inhibition was noted in the presence of similar culture supernatants from five bacilliferous lepromatous leprosy individuals. The results indicate that in contrast to lepromatous leprosy, tuberculoid patients possess antigen reactive lymphocytes which modulate macrophage function through soluble products. Attention is drawn to a rapid and sensitive in vitro method with potential for studying the immunological mechanisms leading to bacterial killing in human leprosy.

Cells, Cultured↗
PubMed1982

The in situ characteristics of mononuclear cell infiltrates in dermal lesions of leprosy.

The in situ nature of mononuclear cell infiltrates in the dermal lesions of 38 untreated leprosy patients was studied by means of conventional surface marker techniques using erythrocytes coated with AET, anti-erythrocyte IgG antibody, hemolysin and complement for the identification of T cells, and cells bearing Fc and C3 receptors, respectively. In general, T cells were the predominant lymphocytes in the leprosy lesions. They were mostly seen to be associated with epithelioid cell granulomas and showed maximal density in tuberculoid leprosy. A graded reduction of T cells was observed in borderline leprosy with a severe reduction/absence in polar lepromatous leprosy. The cells of the mononuclear phagocyte series in the various granulomas of the leprosy spectrum showed the presence of Fc and C3 receptors. Cells bearing a higher density of these receptors had a peripheral localization; whereas cells showing diffuse staining for nonspecific esterase were located more in the central regions of the granulomas. The differences in the individual cells of the phagocytic series appeared to be related to cell maturity; whereas the quantity of T cell infiltration in the lesions showed a correlation with the leprosy spectrum.

Complement C3↗
PubMed1981

Incorporation of 3H-thymidine in Mycobacterium leprae within differentiated human macrophages.

The factors influencing the incorporation of 3H-thymidine (3H-Tdr) in the DNA of Mycobacterium leprae within macrophages derived from human blood have been evaluated. Fifty strains of M. leprae derived from skin nodules of patients with lepromatous leprosy were studied for their ability to incorporate 3H-Tdr. Control macrophages of the same donor maintained alone, or with autoclaved M. leprae, showed low levels of baseline 3H-Tdr incorporation. During a 15-day period of pulsing, 27 of the M. leprae strains incorporated 3H-Tdr at levels of 216-2834% of the incorporation by control cultures. Significant incorporation was observable by the second week of culture and cumulative increases occurred by the third week. A 24-h pulse with 3H-Tdr was inadequate for a detectable increase. A minimal duration of 4-5 days of continuous pulsing was required to obtain a significant increase in the incorporation of 3H-Tdr. Of the 50 M. leprae strains, 23 (46%) failed to incorporate the radiolabel. This failure was apparently not related to differences in the disease status of patients, to the transport conditions for the biopsies, to morphological indices of the extracted M. leprae or to the origin of the host macrophages.

Cell Differentiation↗
PubMed1981

The uptake of 3H-thymidine in Mycobacterium leprae inoculated mouse macrophage cultures as a rapid indicator of bacillary viability. Factors influencing the specificity of the in vitro assay.

Mouse peritoneal macrophages derived from BALB/c were used as host cells for 17 human-derived M. leprae strains. Simultaneous pulsing with 3H-thymidine (3H-Tdr) showed uptake of the radiolabel in 58.8% of the bacilli over a 14 day period. Preliminary data of three M. leprae strains indicate that the 3H-Tdr is preferentially incorporated into the mycobacterial DNA and not into the mammalian host cell DNA. This in vitro assay provides a rapid assessment of M. leprae viability. The factors influencing the uptake of 3H-thymidine are described.

Animals↗
PubMed1980

Reduction of a subset of T cells bearing Fc receptors for IgG in lepromatous leprosy.

Enumeration of a subpopulation of T cells with receptors for the Fc portion of IgG (T gamma) in the peripheral blood of 14 normal subjects and 43 patients with leprosy was undertaken. Tuberculoid leprosy patients showed normal levels of T gamma cells. In contrast, bacillary positive patients with lepromatous leprosy revealed a significant reduction of circulating T gamma cells (p less than 0.001).

B-Lymphocytes↗
PubMed1980

Natural suppressor cells in human leprosy: the role of HLA-D-identical peripheral lymphocytes and macrophages in the in vitro modulation of lymphoproliferative responses.

Six families with HLA-D-identical siblings suffering from leprosy were studied. Lymphocytes and macrophages isolated from the peripheral blood were co-cultured with allogeneic, HLA-D-identical cells and stimulated with M. leprae antigens and concanavalin A. Tuberculoid patients had circulating lymphocytes which showed marked functional suppression of lymphoproliferative responses to antigen and mitogen. In contrast, lepromatous patients showed weak lymphocyte suppressor activity. Macrophages derived from responder individuals augmented, while those derived from lepromatous patients inhibited, M. leprae-induced proliferation of lymphocytes.

Antigens, Bacterial↗
PubMed1980

The suppressive effect of M. leprae on the in vitro proliferative responses of lymphocytes from patients with leprosy.

Peripheral blood lymphocytes from sixty leprosy patients and eight healthy contacts known to be responsive to M. leprae, were stimulated in vitro with concanavalin A (Con A) or PPD alone or in combination with autoclaved, whole M. leprae. Time kinetics and the percentage of inhibition induced by M. leprae differed in the two disease groups and contacts. Antigen-generated suppression of Con A-stimulated lymphocyte transformation was observed on day 4 in seventeen of twenty-one (80%) tuberculoid patients and six of seventeen (35.3%) untreated lepromatous patients. Healthy contacts and 53% lepromatous individuals showed enhanced Con A responses in the presence of antigen. On prolongation of antigen presence to 6 days, a marginal effect was noted in the tuberculoid group. In contrast, all healthy individuals and some lepromatous patients showed increased inhibition of Con A responses. M. leprae antigens showed uniform inhibition of PPD-induced 3H-thymidine incorporation in leprosy patients and healthy contacts.

Antigens, Bacterial↗
PubMed1979

Concanavalin A induced suppressor activity in human leprosy.

Peripheral blood lymphocytes from nine normal subjects and 40 patients with leprosy were pretreated in vitro with Concanavalin A (Con A). Cells from normal subjects pretreated for 24 hours showed consistent and effective generation of suppressive activity which inhibited mitogen induced transformation of autologous lymphocytes. Prolongation of Con A pretreatment to 40 hours resulted in maximal suppressive activity. Tuberculoid leprosy patients had lymphocytes in their blood which on 24 hour pretreatment with Con A exerted suppressive effects markedly greater than the maximal suppression noted with 40 hour pretreated normal lymphocytes. In contrast, untreated patients with polar lepromatous leprosy showed a decrease in suppressive activity which could not be altered by prolongation of Con A pretreatment: the loss of suppressive activity noted in this form of leprosy was restored during erythema nodosum leprosum.

Concanavalin A↗
PubMed1978

The effect of undernutrition on immunological responses to BCG and TAB vaccines in mice maintained on a natural diet.

A study was made on the effect of undernutrition on the immunological responses of mice to TAB and BCG vaccines. The mice were fed a diet comprising chapati and germinated grams; one group was fed ad libitum while another was given half the quantity consumed by the first group. The undernourished mice showed a poor immune response to BCG: only 23% showed a positive reaction to foot pad challenge with purified protein derivative, compared with 76% of the well-fed mice. The mean increase in thickness of the foot pad was also significantly smaller in the undernourished mice. Antibody titres against the H and O antigens of TAB were essentially similar in both groups of mice. The results suggest that undernutrition depresses cell-mediated immune responses but not humoral responses.

Animals↗