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A K Chakravarty

Publications and source records attributed to A K Chakravarty.

At least 37 records · Page 2Linked to original sources
PubMed1986

In vitro analysis of delayed immune response in a bat, Pteropus giganteus: process of con-A mediated activation.

In vitro activation of lymphocytes from the bat, Pteropus giganteus with Con A has been analysed in terms of blastogenesis, DNA synthesis and the effector function, the cytotoxic response. We have observed that lymphocytes of P. giganteus are capable of responding to Con A stimulus and the peak of blastogenesis, DNA synthesis and cytotoxic response have been found at 120 hours with the optimal dose of 10 micrograms X ml-1 Con A; it seems the process of activation in the bat's lymphocytes is delayed compared to this in mice. Significance of this delay in the process of activation of immune response in the bat has been discussed.

Animals↗
PubMed1986

Activation of murine thymocytes in vivo. Part II: Study of blastogenesis, the synthesis of macromolecules and the cytotoxic response after stimulation with phytohemagglutinin.

To determine whether the polyclonal immunomodulator, Phytohemagglutinin (PHA), stimulates murine lymphocytes in vivo and causes cytotoxic differentiation, we studied blastogenesis and the concomitant synthesis of macromolecules (DNA, RNA and protein) by lymphocytes at different hours after injection of PHA in mice. 51Cr release assay was also performed by using allogeneic cells as target to determine whether lymphocytes after stimulation in vivo by this activator undergo cytotoxic differentiation. Out of the five doses of Phytohemagglutinin (2.5 micrograms, 5 micrograms, 10 micrograms, 20 micrograms and 50 micrograms per mouse) a marginally higher peak of blastogenesis was observed with 20 micrograms dose at 48 hr. No significant peak was observed in synthesis of macromolecules or with cytotoxicity.

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PubMed1984

Antibody-mediated immune response in the bat, Pteropus giganteus.

Among mammals, the Chiroptera (Bats) have been perhaps the least studied with respect to systematic accounts of immune responses. To resolve this omission in comparative immunology, we have begun to analyze aspects of immunity of the large frugivorous bat, Pteropus giganteus with respect to antibody secreting plaque forming cells and serum antibodies as measured by haemagglutination titres. Homologous complement was more effective than guinea pig or rabbit complement in lysing SRBC for developing plaques. Kinetic of antibody response to three different doses of SRBC has been studied. We observed a peak primary response and its decay after a single antigenic challenge which were notably delayed, and a same dose of antigen could produce 2-Mercaptoethanol resistant PFC and HA-tires.

Animals↗
PubMed1983

Study of murine lymphoid cells in situ after stimulation with Concanavalin A.

The effects of Concanavalin A (Con A) on the lymphocytes in situ were investigated here by studying the blastogenesis and organization of lymphoid cells in the histological preparations of the spleen and the mesenteric lymph node and the cell death at different hours after iv administration of different doses (10, 20 and 50 micrograms/animal) of the substance. The gradual transformation of the lymphocytes into blasts was observed in the histological preparations of the spleen and the mesenteric lymph node. The rate of the change became higher with higher dose of Con A. It seems that the lymph node was affected more with in vivo Con A treatment than the spleen on account of higher percentage of blast transformation at early hour and lower density of the cells due to cell migration or cell death. Purpose of this study has been discussed.

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PubMed1977

Lectin-driven maturation of cytotoxic effector cells: the nature of effector memory.

In an attempt to define further the activation of effector T-cell function with concanavalin A (Con A), we examined the ability of Con A to generate effector memory in mouse lymph node cells in vitro. In the course of these studies, it became necessary to define parameters by which memory could be defined. These parameters include length of time of exposure to signal required to generate full cytotoxic function; time of onset and kinetics of blast cell formation; requirement for DNA synthesis; sensitivity to the drug 5'-bromodeoxyuridine; and kinetics of the cytotoxic response to alloantigen. By these criteria, mouse lymph node cells exposed 12 days previously to Con A behave qualitatively differently from unprimed mouse lymphocytes. We found that the time of onset and kinetics of DNA synthesis could not be used to distinguish primary and secondary cytotoxic responses. We propose that the parameters defined in these stidues can be applied generally in determining whether a given cytotoxic response involves primed (memory) or unprimed cells.

Animals↗
PubMed1977

An in vitro study of functional maturation of murine thymus cells.

Critical time of onset of thymus cell functions in ontogeny was studied in vitro. Collaborative function in an antibody response and ability to induce a graft-versus-host (GvH) response by murine thymocytes from different stages of ontogeny were investigated. Thymocytes from as early as 16-day mouse embryos were capable of collaborating in the antibody response to sheep-erythrocyte-antigen in vitro following 24 h of pretreatment with concanavalin A (con A). By contrast, maturation of thymus cell function as measured by competence to induce a graft-versus-host reaction, was first manifested by newborn thymus cells, and pretreatment with con A did not facilitate the maturation of this thymus cell function. Experiments to understand the effect of con A on the expression of cell surface antigens have also been reported. Con A-treated thymus cells of different ontogenic stages tested were less susceptible to killing by anti-theta serum than nontreated thymus cells; reverse was true with anti-H-2 serum. The significance of the differential susceptibility of con A-treated thymus cells to anti-sera treatment and the finding that mouse thymocytes can provide helper function as early as the 16th day of gestation have been discussed.

Animals↗
PubMed1976

Activation of cytotoxic function in T lymphocytes.

The requirements for activation of cytotoxic function in mouse T lymphocytes were investigated. Initial generation of cytotoxicity in normal lymphocytes was equal in magnitude with either Con A or specific alloantigen, and in either case required DNA synthesis. Cytotoxic function in MLC-primed cells could also be regenerated by Con A, the magnitude and target specificity of the cytotoxicity thus generated being indistinguishable from that recalled by specific alloantigen. Cytotoxicity could also be regenerated by third party-stimulating cells; however, the cytotoxicity evoked by third party cells was always specific only for target cells of the original stimulating cell H-2 genotype. The data presented suggest that there are a number of ways to activate cytotoxicity in effector T cells, and are most consistent with a model for T cell triggering that minimizes a strict informational function of antigen-receptor interactions.

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