PubMed Health⌕ Search

Biomedical subjects

R K Kumar

Publications and source records attributed to R K Kumar.

At least 109 records · Page 6Linked to original sources
PubMed1986

Characterization of an alveolyn-like protein associated with mouse type 2 pneumocytes using immunochemical methods.

Delipidated proteins from a fraction of mouse lung homogenate enriched for lamellar bodies of type 2 pneumocytes were characterized by a combination of gel filtration and enzyme immunoassay for the presence of a surfactant-associated antigen. Immunoreactivity was associated with a protein of Mr 250-270,000 as well as its multimers and proteolytic fragments. The characteristics of the antigenic protein closely resembled those of a surfactant-associated protein termed alveolyn which is reported to be secreted by type 2 pneumocytes of various other species. Surfactant-associated proteins of M 32-38,000 in bronchoalveolar lavage fluid may be derived from this molecule by proteolysis.

Animals↗
PubMed1986

An enzyme immunoassay for quantitation of a type 2 pneumocyte-specific surfactant-associated antigen in bronchoalveolar lavage fluid.

A sensitive, specific and reproducible assay for quantitation of a surfactant-associated antigen in mouse bronchoalveolar lavage fluid is described. The procedure employed was a non-equilibrium competitive enzyme immunoassay in which detection of unreacted antibody was significantly enhanced by the use of a second antibody and peroxidase-antiperoxidase as the reporter label. The sensitivity of the assay was such that bronchoalveolar lavage fluid had to be diluted 15 to 30-fold prior to assay. No interference by serum proteins or soluble tissue proteins was observed. This assay may provide in vitro quantitative assessment of the functional status of type 2 pneumocytes.

Animals↗
PubMed1986

Altered morphology, growth, and biosynthetic activity of a type 2 pneumocyte-related cell strain induced by lymphokine-enriched supernatants of mitogen-stimulated spleen cells.

Hypertrophy and hyperplasia of type 2 pneumocytes during the evolution of subacute and chronic pulmonary injury cannot always be satisfactorily explained in terms of reparative responses to type 1 pneumocyte injury. We hypothesized that immunocompetent cells, evoked as part of the interstitial inflammatory response, may be secreting factors which affect proliferation and surfactant biosynthesis by type 2 pneumocytes. To evaluate this hypothesis in vitro, we tested the effects of lymphokine-enriched supernatants, from serum-free cultures of concanavalin A-stimulated spleen cells, upon the type 2 pneumocyte-related cell strain NAL 1A. Addition of these supernatants in culture induced irreversible morphologic and ultrastructural alterations in the NAL 1A cells, inhibited cell replication, and evoked increased and apparently abnormal surfactant phospholipid biosynthesis. Supernatants from unstimulated spleen cells had no effect. There was no evidence of toxic injury to the cells in culture, and an immunologically specific cytoplasmic protein continued to be expressed. The active factor(s) appeared to be a protein or peptide of greater than 10,000 molecular weight. A specific soluble factor such as is present in the mitogen-stimulated lymphoid cell supernatants may be capable of mediating a similar interaction with type 2 pneumocytes in vivo.

Animals↗
PubMed1985

Pulmonary responses to bleomycin-induced injury: an immunomorphologic and electron microscopic study.

Intratracheal injection of a small dose of bleomycin in rats induced early alveolar epithelial cell injury and a pneumonitis which subsequently evolved to pulmonary fibrosis. Hydropic degeneration of type I pneumocytes was apparent at 3 days after treatment. Marked interstitial and intra-alveolar pneumonitis developed at 7 days after treatment and was accompanied by hypertrophy and hyperplasia of type II pneumocytes. The inflammatory cell population consisted predominantly of cells with the morphology of large lymphocytes together with a number of eosinophils. Examination by immunoperoxidase and histochemical staining of frozen sections revealed that the lymphoid cells stained positively with the monoclonal antibodies W3/13 and W3/25 but not with other markers. Thus these cells appeared to be helper T lymphocytes. The later development of interstitial fibrosis was accompanied by alveolar microcollapse which contributed to the thickening of alveolar septa observed by light microscopy. The possible role of immunologic and other mechanisms in the pathogenesis of bleomycin-induced pulmonary fibrosis is discussed.

Animals↗
PubMed1985

Expression of a type 2 pneumocyte-specific antigen by a cell strain from normal adult mouse lung.

The mouse lung epithelial cell strain NAL 1A has been confirmed as type 2 pneumocyte-related by immunostaining with a type 2 pneumocyte-specific antiserum. Cytoplasmic immunoreactivity with the antiserum paralleled the appearance of phospholipid-containing osmiophilic cytoplasmic inclusions, which were much more abundant in confluent cell cultures at low passage number than in exponentially growing cultures. However, phospholipid analysis indicated that NAL 1A cells were impoverished in phosphatidylglycerol as compared to lung type 2 pneumocytes. Confluent cultures of the neoplastic cell lines NAL 1AM and NUL 1 did not reveal any reactivity with the specific antiserum.

Animals↗
PubMed1984

Cell separation: a review.

This review summarizes currently available techniques for cell separation. Techniques that exploit differences in physical properties of cells are widely used but have a number of limitations. Those that are based on differences in surface properties may more readily permit reproducible separation of a functionally homogeneous population of cells. Unfortunately very few techniques achieve separation of cells on the basis of differences in their functional characteristics.

Cell Adhesion↗
PubMed1984

Separation and characterization of lymphocytes from rat lung parenchyma.

Rat pulmonary parenchymal tissue was disaggregated into a single cell suspension by treatment with collagenase. A cell population enriched for lung lymphocytes was separated by depletion of adherent cells on a Sephadex G-10 column: 16.7 +/- 2.7 X 10(6) cells per animal were recovered. On the basis of cytochemical and morphologic criteria, the separated cells contained greater than 80% lymphocytes, with a viability of 80-90%. The distribution of lymphocyte subpopulations was determined by indirect immunoperoxidase staining with appropriate monoclonal antibodies. Separated lung lymphocytes exhibited a proliferative response in vitro to phytohemagglutinin and concanavalin A. Supernatants from lung lymphocytes stimulated with concanavalin A contained lymphokine activity that could be demonstrated in a leukocyte procoagulant activity assay.

Animals↗
PubMed1982

Escape of tumours from immunological destruction.

This paper reviews the mechanisms of tumour escape from immune destruction that have been delineated in the past 2 decades. Current evidence indicates that the principal escape mechanisms are (i) weak or absent immunogenicity (ii) immunosuppression by tumour antigens or antigen-antibody complexes (iii) induction of suppressor cells and (iv) production of immunosuppressive factors. A classification of tumour escape mechanisms is presented.

Aged↗
PubMed1981

Immunosuppression associated with SJL/J murine lymphoma. I. Suppression of cell-mediated immune responses after tumor transplantation.

The proliferative responses of peripheral blood lymphocytes of inbred SJL/J mice to the mitogens phytohemagglutinin and concanavalin A were evaluated serially in individual animals before and after induction of lymphomas by transplantation. Tumor-bearing mice exhibited marked suppression of mitogen responsiveness. Proliferative responses in mixed lymphocyte-tumor cell culture and mixed lymphocyte culture were also suppressed. Suppression of responses was tumor related, and responsiveness was restored in animals whose tumors regressed. There was no deficiency of responder T-cells in the peripheral blood of tumor-bearing animals, and suppressor cell activity was not demonstrable in a number of in vitro assays. However, plasma from tumor-bearing animals exhibited potent immunosuppressive activity. The presence of plasma suppressive activity was similarly tumor related. Thus this study demonstrates nonspecific suppression of cell-mediated immune responses following tumor induction, apparently mediated by a plasma suppressor factor.

Animals↗
PubMed1981

Immunosuppression associated with SJL/J murine lymphoma. II. Characterization of a plasma suppressor factor in tumor-bearing mice.

The properties of a factor responsible for immunosuppressive activity in the plasma of inbred SJL/J mice bearing transplanted lymphomas were investigated. Suppressive activity was not due to an intact virus but resided in a soluble molecule characterized as a nonimmunoglobulin protein of molecular weight 68,000-88,000. The plasma suppressor factor was relatively stable and was neither directly cytotoxic nor complement-dependent. The degree of suppression of in vitro lymphocyte proliferative responses depended on the time of addition of plasma to cultures. Suppression was reversible if cells exposed to plasma were washed before mitogen stimulation, but stimulated cells exposed to the suppressor factor were irreversibly inhibited. The suppressor factor was partially species-specific. Supernatants from short-term cultures of tumor cells from lymph nodes of SJL/L mice contained a similar suppressor factor, indicating that the plasma factor was probably a product of tumor cells.

Animals↗
PubMed1979

A micromethod for in vitro assay of lymphocyte proliferation in mouse whole blood.

A microplate culture system to assay the in vitro proliferative responses of mouse peripheral blood lymphocytes to phytohaemagglutinin is described. The method utilises whole blood, a gamma-emitting isotopic label and semi-automated harvesting. Data are presented to show the effects of several variables on the culture system. The technique is suitable for serial study of the in vitro phytohaemagglutinin response in individual animals.

Animals↗