• R K Saxena

      Articles written in Journal of Biosciences

    • Comparison of murine B-cell proliferative response to bacterial lipopolysaccharide and DNP derivative ofMycobacterium tuberculosis antigens

      Anila Prabhu R K Saxena

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      The DNP derivative of sonicate antigens of the H37Ra strain ofMycobacterium tuberculosis (Ra-DNP) is known to induce marked B-cell proliferation. In order to understand whether B-cell proliferation in response to Ra-DNP was antigen driven or represented a non-specific mitogenic effect of Ra-DNP, the effect of Ra-DNP was compared with that of lipopolysaccharide a potent B-cell mitogen. Parameters used for comparison were (i) thymidine incorporation, (ii) viable cell counts, (iii) amount of lg secreted, (iv) isotype profile of Ig released and (v) cell cycling pattern of B-cells in culture. Overall the effect of Ra-DNP was found to be essentially similar to that of lipopolysaccharide for all parameters examined. Yet quantitatively, the effect of the former was always relatively poorer. At optimal doses, the effect of Ra-DNP ranged from 50 to 70% of the lipopolysaccharide effect in different assays. These results suggest that Ra-DNP may have a B-cell mitogenic effect similar to the effect of lipopolysaccharide, but all B-cells may not respond to Ra-DNP.

    • Enhanced MHC I antigen expression on tumour target cells is inversely correlated to lysis by allogenic but not by xenogenic NK cells

      A Sarin Q B Saxena R B Herberman R K Saxena

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      Relationship between the levels of MHC class 1 antigen expressed on tumour cells and their susceptibility to allogenic and xenogenic NK cells was investigated. Mouse and human natural killer-resistance inducing factor (NK-RIF) preparations were used for augmenting/inducing MHC 1 antigen expression on murine YAC and human K562 tumour cells, respectively YAC cells with augmented MHC I antigen expression became relatively resistant to lysis by murine NK cells but not to rat NK cells. Similarly, induction of MHC I antigens on K562 cells reduced their susceptibility to human NK cells but not to monkey NK cells. These results indicate that the inverse correlation of MHC I antigen expression and NK susceptibility does not hold true for xenogenic pairs of NK effector and target cells.

    • Partial purification and characterization of a novel human factor that augments the expression of class I MHC antigens on tumour cells

      R K Saxena Q B Saxena T L Whiteside R H Goldfarb R B Herberman

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      A cytokine which augments the expression of major histocompatibility complex (MHC) I antigens on K562 and gastric carcinoma tumour (HR) cells, has been isolated from the culture supernatant of Concanavalin-A (Con-A) activated human peripheral blood mononuclear cells. The factor, termed MHC augmenting factor (MHC- AF) has been partially purified by Sephadex G- 100 column chromatography, preparative isoelectric focusing and HPLC with ion- exchange as well as sizing columns. MHC-AF activity is associated with a 35 kDa molecule which has pI of 6.0. Interferon (IFN)-α, \, tumour necrosis factor (TNF), Interleukin (IL)-2, IL-4, IL-5 and IL-7 had no significant effect in MHC- AF bioassay, but IFN-γ had significant MHC-AF activity. Antibodies to IFN-α, IFN-\ and TNF-α did not block the activity of MHC-AF, but anti-IFN-y antibodies could partially neutralize the activity. However, unlike IFN-γ, MHC-AF activity was resistant to pH 2.0 treatment. Purified MHC-AF preparations did not have any activity in WISH cell/encephalo myocarditis virus (EMC) IFN bioassays. In addition, anti-IFN-y affinity column did not retain MHC-AF activity. These results indicate that a MHC-AF distinct from IFN-γ, is produced by activated human mononuclear cells.

    • Generation of human class I major histocompatibility complex activating factor in serum free medium and its partial characterization

      Aparna Raval Niti Ipuri R K Saxena

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      Human peripheral blood mononuclear cells (PBMCs) activated with Con-A release a soluble factor which augments the expression of class I major histocompatibility complex (MHC) antigens by a variety of tumour cells. Previous attempts to purify this factor called MHC-activating factor (AF) (MHC-AF) made us realize that the presence of large numbers and quantities of irrelevant fetal calf serum proteins in the culture supernatants of the activated human PBMCs, interfered with the purification procedure. It was therefore necessary to standardize the use of a serum free culture medium to generate human MHC-AF. In the present communication we have tried several types of culture media and have identified DCCM-2 as the most suitable culture medium to generate human MHC-AF. MHC-AF generated in DCCM-2 medium appears to be a protein molecule resistant to pH 2 treatment but sensitive to heat treatment (56°C × 45 min) and treatment with proteolytic enzymes trypsin and chymotrypsin.

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