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Biomedical subjects

A Landay

Publications and source records attributed to A Landay.

87 records · Page 5Linked to original sources
PubMed1986

Flow cytometry evaluation of cell-mediated cytotoxicity.

A novel flow cytometry method for the evaluation of cell-mediated cytotoxicity is described. This method uses flow cytometry analysis to distinguish target cells from effector cells by differences in volume and light scatter characteristics. Non-viable target cells, following their interaction with effector cells, are determined via propidium iodide (PI) dye exclusion and then expressed as a percentage of the total target cell population. This assay is suitable both for analysis of systems which allow recycling of cytotoxic effector cells (total cell cytotoxicity assays, TCCA), and of systems in which recycling does not occur (single cell cytotoxicity assays, SCCA). Natural killer (NK) cell-mediated cytotoxicity evaluated by flow cytometry is significantly correlated with the standard 51Cr release assay. Flow cytometry can also be used to evaluate the competitive inhibition that certain cell types exert on the cell-mediated killing of NK-sensitive targets. A prerequisite for this assay is that competitor cells and target cells are distinguishable through their volume and light scatter characteristics. Advantages and pitfalls of the flow cytometry method are discussed, in comparison with the 51Cr-release assay.

Adult↗
PubMed1986

Idiotypic analysis of a B cell clone with anti-intermediate filament specificity in a patient with Sjögren's syndrome: involvement of five subpopulations producing different immunoglobulin isotypes.

An IgM paraprotein from patient LP with Sjögren's syndrome exhibited an antibody activity to intermediate filaments (IMF) of cells from all vertebrates examined, and appeared to recognize several classes of IMF (i.e., vimentin, desmin, and keratin). A mouse monoclonal anti-idiotype (Id) antibody, K4A, was prepared against the IgMk (LP) and used as a specific probe in two-color immunofluorescence to examine the extent of clonal involvement in the patient's blood and bone marrow mononuclear cells (MNC). Twenty to 30% of MNC in her blood samples were IgMk+ plasmablasts with morphologic similarity to Waldenström's macroglobulinemia cells. IgG+ and IgA+ plasmablasts were demonstrated in lower frequencies (approximately 2%). Almost all of the IgM+ cells and approximately 80% of the IgG+ cells and IgA+ cells in the blood were reactive with the K4A anti-Id antibody. Immunoglobulin (Ig) subclass analysis revealed that the K4A Id was expressed by IgG1+, IgG3+, IgA1+ and IgA2+ plasmablasts. Similar observations were obtained with bone marrow samples, although the proportion of Id+ cells among IgG+ or IgA+ cells was lower in marrow than in blood. IgG and IgA fractions isolated from the patient's serum were also shown to contain anti-IMF activity. Ig biosynthetic analysis of blood MNC revealed that the K4A anti-Id antibody precipitated not only IgM but also IgG and IgA. Because cells simultaneously producing two different Ig isotypes were not detected, these results indicate the presence of five separate subpopulations of the K4A Id+ neoplastic clone. The data thus suggest the occurrence of a neoplastic or pre-neoplastic transformation event before the switching of Ig heavy chain isotypes, and imply a role for the IMF antigen in the exaggerated proliferation and differentiation along five of the nine potential intraclonal pathways.

Animals↗
PubMed1985

A human B cell differentiation antigen selectively expressed on mature B cells identified by a monoclonal antibody (HB-2).

A monoclonal IgM antibody (HB-2), produced against a membrane antigen on the Raji, B cell line, reacted by indirect immunofluorescence with 2 to 40% of lymphoblasts from the B cell lines, Raji, Daudi, SN-1036, and SB but not with other types of cell lines, including pre-B, myeloid, melanoma, or T cells. HB-2 antibody reacted with 10 +/- 3% of normal blood mononuclear cells, and was unreactive with monocytes, granulocytes, platelets, or erythrocytes. Two-color immunofluorescence revealed that HB-2 antigen expression was confined to cells bearing surface Ig. An interesting finding was the fact that 25% of plasmablasts induced by pokeweed mitogen also expressed the HB-2 antigen. However, pre-B and plasma cells from normal bone marrow did not express the HB-2 antigen either on their membrane surface or in their cytoplasm. Analysis of 85 leukemias revealed that the HB-2 antigen was expressed on acute and chronic B cell leukemias and Burkitt's lymphomas, but not on malignancies of pre-B, T, myelocytic, or plasma cells. The results suggest that expression of the HB-2 antigen is confined to mature B cells.

Antibodies, Monoclonal↗
PubMed1984

A lymphoproliferative disorder of granular lymphocytes with a novel phenotype and suppressor function.

In this study we have identified and characterized an expanded granular lymphocyte population in a patient with anemia and granulocytopenia. Granular lymphocytes were identified through the presence of cytoplasmic azurophilic granules, the dispersed granular pattern of cytochemical staining for acid hydrolases, and the ultrastructural localization of acid phosphatase within the granules. The surface phenotype of the granular lymphocytes was E+, FcR-, Leu 4+, Leu 2+, D 12+ (Leu 15+), OKM1+, and Leu 7+. This phenotype has not been reported previously in patients with similar features. Functional studies on FACS-purified populations showed that the patient's granular lymphocytes responded poorly to T-cell mitogens and were inefficient in NK and ADCC assays but exerted a potent suppressor effect on both T-cell proliferation and B-cell differentiation. The phenotype and functions of the expanded granular lymphocyte population correspond to those of a subset of normal E rosette-forming granular lymphocytes.

Adult↗
PubMed1984

Characterization of human lymphocyte subpopulations: alloreactive cytotoxic T-lymphocyte precursor and effector cells are phenotypically distinct from Leu 2+ suppressor cells.

The OKT8/Leu 2+ human T-cell subset contains cells which perform suppressor and cytotoxic functions. We have recently produced two monoclonal antibodies (termed 2D2 and D12) which define four subpopulations of human E+ cells. Previous studies have shown that the Leu 2+ cells that suppress T-cell proliferative responses have the 2D2+D12+ phenotype. In the present studies, we have used these antibodies and fluorescence-activated cell sorter techniques to characterize the phenotype of cytotoxic T lymphocytes generated in allogeneic mixed lymphocyte cultures. These studies indicate that the cytolytic effector cells which recognize class I major histocompatibility antigens express the 2D2+D12- phenotype. The phenotype of the precursor cells for these cytotoxic T cells was similarly demonstrated to be 2D2+D12-. The subset of E+ cells with NK cytolytic activity expressed the 2D2-D12+ phenotype. These data demonstrate that the Leu 2+ precursor and effector cytotoxic T cells reactive against class I alloantigens are phenotypically distinct from the Leu 2+ cells previously shown to suppress T-cell proliferative responses.

Antibodies, Monoclonal↗
PubMed1984

Phenotypically and functionally distinct subpopulations of human lymphocytes with T cell markers also exhibit different cytochemical patterns of staining for lysosomal enzymes.

Human peripheral blood lymphocytes that express T cell markers, when reacted for the cytochemical localization of lysosomal acid hydrolases, display two major patterns of staining, i.e., dot-like and scattered granular. Previous attempts to fractionate T cells according to surface markers have yielded populations of cells with heterogeneous patterns of cytochemical staining. In this study, peripheral blood cells forming rosettes with sheep erythrocytes have been fractionated by sequential staining with two monoclonal antibodies, D12 and 2D2, followed by fluorescence-activated cell sorting. These reagents have been shown previously to recognize a subpopulation of cells capable of suppressing T cell proliferation. All of the cells positive for D12 and 2D2 stained for acid hydrolases with the scattered granular pattern, whereas the large majority of the cells negative for both markers stained with the dot-like pattern. It is concluded that suppressor cells within the E+ cell fraction have the cytochemical characteristics of large granular lymphocytes.

Acid Phosphatase↗
PubMed1983

Antibodies to human T-cell leukemia virus membrane antigens (HTLV-MA) in hemophiliacs.

Along with homosexual men, Haitians, and intravenous drug abusers, hemophiliacs are at high risk of contracting acquired immunodeficiency syndrome (AIDS). An earlier study revealed that 36 percent of a group of the AIDS patients had antibodies to cell membrane antigens associated with the human T-cell leukemia virus (HTLV-MA), whereas only 1.2 percent of matched asymptomatic homosexual controls had these antibodies. In the present experiments, serum samples from 172 asymptomatic hemophiliacs were examined for the presence of antibodies to HTLV-MA. Such antibodies were detected in 5 to 19 percent of the hemophiliacs examined from four geographical locations, but in only 1 percent or less of laboratory workers, normal blood donors, donors on hemodialysis, or donors with chronic active hepatitis.

Antibodies, Viral↗
PubMed1983

Enumeration of human lymphocyte subpopulations by immunofluorescence: a comparative study using automated flow microfluorometry and fluorescence microscopy.

These studies reveal that the enumeration of peripheral blood mononuclear cells by fluorescence microscopy and automated flow microfluorometry show a high degree of correlation whether the cells came from normals, individuals with common variable immunodeficiency, chronic lymphocytic leukemia of B cell origin or chronic lymphocytic leukemia of T cell origin. There was excellent agreement between these two methods when counting positive cells stained by the pan-T monoclonal antibodies OKT3 and Leu-1, the helper T reagents OKT4 and Leu-3a, and the suppressor T antibodies OKT8 and Leu-2a. The values obtained for B cells using a pan-B (HB-2) cell antibody analyzed by fluorescence microscopy and automated flow microfluorometry gave a correlation coefficient of 0.86. The percentage of cells identified by antibodies with reactivities toward peripheral blood monocytes (MMA or Leu-M1), the HLA-DR determinant, and HNK-1 (Leu-7) positive cells gave correlation coefficients of 0.90, 0.90, and 0.80 respectively when compared by the 2 methods mentioned above. These data suggest that comparable values for lymphocyte subpopulations in human blood samples can be obtained using the most convenient and available technology.

Antibodies, Monoclonal↗
PubMed1983

Immunologic studies in asymptomatic hemophilia patients. Relationship to acquired immune deficiency syndrome (AIDS).

Asymptomatic hemophilia patients receiving Factor VIII concentrate were found to have normal natural killer (NK) cells and B cells, and an inverted T helper/suppressor ratio due to an increase in cells of T suppressor phenotype. In contrast, a hemophilia patient with acquired immune deficiency syndrome (AIDS) exhibited nonfunctional NK cells, low B cells, and an inverted T helper/suppressor ratio due to very low numbers of T helper cells. Hemophilia patients on cryoprecipitate therapy exhibited normal immune parameters. A high percentage of hemophilia patients on both treatments had antibody to hepatitis B virus. The isolated finding of elevated levels of T suppressor cells in hemophilia patients receiving Factor VIII concentrate has not been recognized as an early indicator of impending AIDS, and longitudinal studies will be required to determine its clinical significance.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Acquired immunodeficiency syndrome with Pneumocystis carinii pneumonia and Mycobacterium avium-intracellulare infection in a previously healthy patient with classic hemophilia. Clinical, immunologic, and virologic findings.

A previously healthy patient with classic hemophilia who was on a home infusion program with factor VIII concentrates developed an acquired immunodeficiency syndrome manifested by a dramatic weight loss (47 kg over 12 months), lassitude, transient thrombocytopenia, and opportunistic infections with Varicella zoster, Pneumocystis carinii, and Mycobacterium avium-intracellulare. The patient was not homosexual and had no history of intravenous drug abuse. Immunologic studies showed a persistent lymphopenia with reversal of helper/suppressor-cytotoxic T-lymphocyte ratios, depression of human natural killer cell function, and in-vitro lymphocyte proliferative responses to mitogens and viral antigens. Serum IgA levels were also elevated. Serum antibodies against cytomegalovirus, herpes simplex viruses 1 and 2, Epstein-Barr virus, Varicella zoster, and hepatitis B virus were shown, suggesting previous infection by these agents. Reactivation of cytomegalovirus infection was suggested by a rising titer of antibodies against cytomegalovirus concurrent with pneumocystis pneumonia, and was confirmed by the growth of this virus in a throat culture 2 months later.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Characterization of a phenotypically distinct subpopulation of Leu-2+ cells that suppresses T cell proliferative responses.

Two new monoclonal antibodies (termed 2D2 and D12) have been used to identify and to analyze phenotypically distinct subpopulations of human T cells. The 2D2 antibody recognized an antigenic determinant closely related, if not identical, to that reactive with the anti-Leu-2 monoclonal antibody. The D12 antibody reacted with a variety of cell types, which included a subpopulation of Leu-2+ (2D2+) T cells. These antibodies were used to isolate four phenotypically distinct T cell populations by sequential cell sorter techniques. Functional analyses demonstrated that the 2D2+D12+ subset was unique in its ability to suppress the antigen-induced proliferation of T cells. These cells also suppressed the proliferative responses of other T cell subsets stimulated with mitogens. Pretreatment of 2D2+D12+ T cells with mitomycin C before culture abrogated the suppressor cell activity of these cells. We propose that the cells within the Leu-2+ cytotoxic/suppressor T cell subpopulation that suppress T cell proliferation are phenotypically distinct and express the 2D2+D12+ membrane antigenic phenotype.

Animals↗
PubMed1983

Immunogenetic and immunologic aspects of gliosarcoma growth in rats.

Growth of the chemically induced, transplantable rat brain tumor gliosarcoma 9L (GS-9L) is under immunogenetic control. Both susceptible and resistant rats produce an immune response to the tumor, but the response is qualitatively different in the two groups. The intraperitoneal administration of gliosarcoma-9L cells in resistant KGH rats causes the production of cytotoxic lymphocytes and macrophages, and in susceptible F344 rats suppressor lymphocytes are produced. After gliosarcoma-9L cells were administered to (KGH x F344)F1 and backcross rats, tumor susceptibility or resistance and the nature of the immune response correlated well with the histocompatibility type, indicating the parallel genetic control of both traits. However, a second gene or gene complex, not linked to the major histocompatibility complex, may participate in the regulation of tumor growth.

Animals↗
PubMed1979

Effect of total body temperature on toxicity of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU).

One hundred eighty-two rats were divided into groups to test the effect of three different total body temperature levels on the toxic effect of three different dose levels of 1,3-bis(2-chlorethyl)-1-nitrosourea (BCNU) and to assess the effect of delayed total body temperature elevation on BCNU breakdown products. Results were tabulated on the basis of life survival figures. At depressed total body temperatures (28 degrees C), normally expected toxicity was avoided. Elevated body temperatures, on the other hand, enhanced the toxic effect of BCNU. Delayed total body temperature elevation (3 and 6 days after BCNU administration) created similar toxicity. This finding was not observed when total body temperature elevation was delayed 10 days. The results point toward an interesting interaction between BCNU and heat (immediate and delayed) on the basis of an elevated metabolic rate of tissue, a synergistic effect of two therapeutic modalities, interference with normal reparative processes by the combination, or an enhancement of retained serum protein-bound breakdown products of BCNU.

Animals↗
PubMedDate not supplied

Experimental evaluation of nonspecific immunostimulation and chemotherapy in the intracranial tumor-bearing Fisher rat.

One hundred sixty rats bearing intracranial tumors were divided into groups of 10 to evaluate C-I interval +, effect of chemotherapy alone (BCNU), chemotherapy and C. parvum, and C. parvum alone in the rat tumor model. All therapy was administered intraperitoneally: BCNU -5.2 mg/kg (40% of LD10) on the 9th and 16th post tumor implant day, and C. parvum-1.4 mg regardless of the body weight and the 6th or 23rd day and 6th and 23rd post tumor implant day. An additional group received BCNU on the 9th and 16th day and C. parvum every 3rd day beginning with the 11th post implant day. It is concluded that C. parvum given before BCNU yields the greatest increase in survival in this animal system. Two or more injections were detrimental and injections after BCNU were of less value. C. parvum alone was minimally effective. If nonspecific immunostimulation is contemplated in this animal tumor system, it would appear to be best given before chemotherapy. This may relate to the brain as a "privileged immune site", or a peculiarity of the blood brain barrier in an intracranial lesion as it related to combined therapy.

Animals↗