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Results for “Immunologic Capping”

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At least 775 records · Page 43Linked to original sources
PubMed1983

Resting and activation antigens of T cells: studies with OKT10 and OKT20 monoclonal antibodies.

OKT10 and OKT20 are monoclonal antibodies that recognize cell surface antigen(s) on resting thymocytes, plasma cells, null cells, monocytes, and some bone marrow cells. The respective antigens, poorly expressed on resting peripheral T cells, are strongly expressed on T cells activated either in vitro or in vivo. Double-staining experiments using either OKT10 or OKT20, in combination with OKT3, provided paradoxical results. If indirect staining with OKT3 plus horse alpha-mouse IgG preceded staining with OKT10 or OKT20, most cells showed double staining; all other staining sequences yielded the expected result that OKT3+ cells expressed very little OKT10 or OKT20. Analysis of the experiments revealed that perturbation of the cell membrane with a monoclonal antibody reactive with a cell surface antigen (for example, OKT3) followed by a crosslinking second antibody caused the expression of these antigens. This suggests that these antigens, normally expressed on activated T cells, are actually present in an unexpressed form within the membrane of resting T cells.

Animals↗
PubMed1984

[Change in the turnover of HLA ABC molecules in circulating T lymphocytes in mycosis fungoides].

The turnover of HLA ABC molecules at T and B lymphocyte surface was analyzed in five cases with mycosis fungoides and six healthy controls. The patients had only skin lesions and are staged from T1 to T3 and No, Bo and Mo. The turnover was analyzed by mean of the decrease of the lysis by complement on sensitisized cells with anti HLA ABC antibodies that were incubated for progressive times at 37 degrees C. The results show a largest turnover for the HLA ABC molecules all T cells surface from mycosis fungoides that was significant (PWilcoxon less than 0.01). The turnover of B cells surface was not different from mycosis fungoide and healthy controls. The observed phenomenon was not specific for mycosis fungoide or T cells because previously has been shown in others lympho-proliferative and autoimmune diseases. The authors suggest that the analyzed T lymphocyte, morphologically normal is functionally altered and the behavious could be a metabolic phenotypic marker for the T cell before his coming at skin lesions.

Adult↗
PubMed1984

The antigen of mature human B cells detected by the monoclonal antibody FMC7: studies on the nature of the antigen and modulation of its expression.

The monoclonal antibody FMC7 delineates a subpopulation of B lymphocytes in normal blood. Expression of the antigen recognized by FMC7 appears to be maturation-linked, and it serves to distinguish different types of B cell leukemia. The data presented here indicate that the antigen is a protein that is integrated in the cell membrane and that is able to interact with the cytoskeleton. The antigen is rapidly synthesized and turned over, is not cell cycle-dependent, and is relatively resistant to changes induced by culture in the presence of a phorbol ester.

Antibodies, Monoclonal↗
PubMed1983

A unique antigen expressed on myeloid cells and acute leukemia blast cells defined by a monoclonal antibody.

A murine hybridoma-derived monoclonal antibody, PM-81, was obtained from a fusion of cells of the NS-1 myeloma cell line with cells from a mouse immunized with the HL-60 promyelocytic leukemia cell line. This cytotoxic IgM monoclonal antibody was specific for myeloid cells. Employing indirect immunofluorescence and flow cytometry, we determined that this antibody reacts strongly with normal human granulocytes, eosinophils, and monocytes but not lymphocytes (including phytohemagglutinin-activated lymphocytes), null cells, red blood cells, or platelets. Moreover, the PM-81 antibody reacts with leukemia cells from 19 of 22 patients with acute myelocytic leukemia of all FAB subclasses, three of three patients with common acute lymphocytic leukemia, four of four patients with chronic myelocytic leukemia (CML) in myeloid blast crisis (terminal transferase (TdT)-negative) but did not react with cells from two patients with CML in lymphoid blast crisis (TdT-positive) or five patients with chronic lymphocytic leukemia. The myeloid cell lines HL-60, K562, KG-1, and U937 were all reactive with PM-81. The lymphoid lines CCRF-CEM and Daudi did not express PM-81 but HSB-2 was positive. The PM-81 antigen was absent on myeloid and erythroid progenitor cells as determined by their insusceptibility to complement-dependent lysis. In addition, only PM-81-unreactive cells were capable of colony formation. Furthermore, the PM-81 antibody does not appear to induce modulation of the antigen to which it binds. Thus, this monoclonal antibody appears to fulfill several criteria for clinical utility in the diagnosis and treatment of both acute myelocytic and acute lymphocytic leukemia.

Animals↗
PubMed1983

Activation of antigen-enriched B cells. II. Role of linked recognition in B cell proliferation to thymus-dependent antigens.

The responsiveness to T-dependent (TD) and T-independent (TI) TNP-antigens of murine splenic B cells previously enriched for antigen-binding cells (ABC) was examined. TNP-TI antigens induced B cell proliferation. TNP-TD antigens did not induce a proliferative response regardless of the physical form or nature of the TNP-TD antigen (e.g., soluble vs particulate, low or high haptenation of carrier, TNP on various insoluble matrices, etc.). TNP-TD antigens were effective in enhancing the response of the TNP-ABC to all concentrations of lipopolysaccharide (LPS) tested, indicating that binding of antigen to surface immunoglobulin alters the LPS responsiveness of the cell. Irradiated, keyhole limpet hemocyanin- (KLH) primed T cells induced a threefold to fourfold greater B cell proliferative response with TNP-KLH than with fluoresceinated KLH (FLU-KLH) or FLU-KLH together with TNP-human serum albumin (TNP-HSA). Therefore, linked recognition appears essential for optimal T cell-mediated B cell proliferation, whereas the induction of B cell proliferation via nonlinked, carrier-activated T cells is a minor component of the response.

Animals↗
PubMed1981

Multiple heavy chain isotypes on the membrane of the small B lymphocytes in human blood.

Small lymphocytes from adult human blood were examined for the presence of membrane-associated alpha, gamma, delta and mu Ig isotypes by means of a direct immunofluorescence technique. Since less than 10% of the small lymphocytes in blood are B cells as defined by positive reactivity with an anti-Fab conjugate, our experiments were performed on a T cell-depleted fraction in which about 80% of the small lymphocytes were B cells. With the two-wavelength immunofluorescence method, all of the double-isotype combinations were found. The percentage of cells bearing more than two isotypes was deduced. The delta mu and the alpha delta mu combinations were the most common, as previously found on tonsillar lymphocytes. In contrast with the tonsils, no lymphocytes bearing only delta were observed and the proportions of alpha gamma- and alpha gamma mu-bearing lymphocytes were very small. The presence of lymphocytes bearing four isotypes could practically be excluded.

Adult↗
PubMed1982

Loss of surface-bound antibody accompanying the anti-complementary modulation of leukemic B cell immunoglobulin: contrasting effects of antibodies directed against idiotypic and constant regions.

Guinea pig L2C leukemic lymphocytes display at their surfaces monoclonal IgM, which when compared with antibody undergoes rapid redistribution and variable endocytosis. One consequence of this is that the cells can prove resistant to lysis by complement subsequently added to the system, a process termed here anti-complementary modulation. We studied quantitatively the extent of antibody loss accompanying the modulation by radioimmunolabeling the cell surfaces with 125I-Fab' gamma fragments from an anti-antibody. Antibody directed against the constant region of the IgG light chain (anti-lambda) gave modulation effective against syngeneic (guinea pig strain 2) complement that closely paralleled the disappearance of anti-lambda from the cell surfaces. Antibody directed against the idiotypic region of the light chain (anti-Id) was as effective as anti-lambda in modulating against syngeneic complement. However, the bulk of the anti-Id was seen by radioimmunolabeling to persist on the surfaces of the resistant cells, even after prolonged exposure at 37 degrees C, and was shown by immunofluorescence to be in a patched configuration. In contrast to the results with syngeneic complement, modulation effective against rabbit complement appeared to have an absolute requirement for clearing of the antibody: thus anti-lambda could modulate, anti-Id could not. The differences observed between anti-lambda and anti-Id could not be accounted for by differences in their isotypic (Ig subclass) composition nor by the numbers of antibody molecules bound. Studies with directly fluoresceinated and 125I-labeled anti-lambda revealed endocytosis rather than shedding was the major route of antibody loss from the cell surfaces over the period of anti-complementary modulation. The findings are discussed in relation to mechanisms that enable leukemic B lymphocytes to escape destruction when confronted by antibody and complement.

Animals↗
PubMed1980

Indirect rosette microassay to characterize human melanoma-associated antigens recognized by operationally specific xenoantisera.

The indirect rosette assay which detects the interaction of antibodies with target cells by their ability to rosette with sheep red blood cells chemically coated with purified anti-immunoglobulin antibodies or with protein A from Staphylococcus aureus has been used to analyze xenoantisera to human melanoma-associated antigens. The test has been developed as a microassay and performed in microtiter plates, thus facilitating the screening of large numbers of samples. When modified as an inhibition assay, the assay has been successfully used (a) to compare the specificities of xenoantisera elicited with cultured melanoma cells, hybrids derived from the fusion of cultured human melanoma cells, and murine fibroblasts and melanoma-associated antigens purified by biochemical procedures and (b) to investigate the relationship of melanoma-associated antigens with beta 2-microglobulin and HLA antigens on the membrane of melanoma cells.

Antibodies, Anti-Idiotypic↗
PubMed1982

H-2 and viral haemagglutinin expression by influenza-infected cells; the proteins are close but do not cocap.

The proximity of H-2K and D antigens and influenza virus haemagglutinin (HA) molecules on the surface of infected target cells was assessed by a topographical study using monoclonal antibodies to H-2 and to HA. The effect of pretreatment of fixed, infected cells with excess of one monoclonal antibody on the subsequent binding of a second radiolabelled antibody was measured. Using CBA mouse B lymphoblasts which were paraformaldehyde fixed 5 hr postinfection with influenza virus (A/USSR/90/77), pretreatment with monoclonal antibody 30/3 to H-2Kk and Dk partially blocked (Approximately equal to 37%) the binding of one radiolabelled monoclonal anti-HA antibody (264/2). A different monoclonal IgG (W18/1) directed to the same HA molecule was not blocked by similar pretreatment of cells with the anti-H-2 antibody. Interaction of monoclonal antibodies with their sites is highly specific, and mutual blocking of two antibodies requires very closely located sites even if the antibodies are directed to the same molecule. We therefore have evidence for proximity of H-2 and HA molecules; however, we were unable to demonstrate cocapping of H-2K and D antigens with influenza HA.

Animals↗
PubMed1980

The bovine lymphoid system. III. A monoclonal antibody specific for bovine cell surface and serum IgM.

Mouse spleen cells from animals immunized with bovine peripheral blood lymphocytes were fused to X63 . Ag8 myeloma cells and the activity of one of the resulting myeloma hybrids was characterized. The product of this clone (B5/4.1.4) binds to pentameric bovine IgM isolated from serum but not to serum IgG1 or IgG2. This reagent also binds to cell surface (monomeric) IgM and can be used in immunofluorescence assays to enumerate IgM-bearing cells in lymphoid cell suspensions and to examine B lymphocytes or B lymphocyte derived cells in tissue sections.

Animals↗
PubMed1981

Different efficiency of mercurascan in allograft survival prolongation in male and female mice.

The efficiency of mercurascan on prolongation of skin allograft survival was found to depend on the sex of experimental animals. Long-term treatment of the recipients by MSC in the mouse strain combination B10--B10.LP (donor X recipient, difference in non-H-2 loci) was more efficient in females than in males. The immunosuppressive effect of MSC was weak. MSC had no effect on the survival time of skin or heart allografts in a strain combination with limited H-2 differences [B10.D2--M(504)]. The effect of MSC on the cell membrane was followed in vitro by measurement of the rate of H-2 antigen redistribution on lymphoid cells of animals treated in vivo by MSC. The rate of redistribution on lymphoid cells from MSC-treated females was decreased; no effect was observed in the case of cells from treated males.

Animals↗