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Biomedical subjects

E S Vitetta

Publications and source records attributed to E S Vitetta.

At least 343 records · Page 19Linked to original sources
PubMed1974

Cell surface immunoglobulin. VII. Synthesis, shedding, and secretion of immunoglobulin by lymphoid cells of germ-free mice.

Lymphoid cells from the spleen, lymph nodes, and thoracic duct of axenic and control mice were incubated with [(3)H]tyrosine and synthesis and secretion of protein and Ig studied. It was found that only IgM was synthesized by cells from axenic mice whereas cells from control mice also synthesized IgG. Splenocytes from both axenic and control mice had 8S IgM on their surface. Radiolabeled splenocytes from axenic mice were incubated to determine the kinetics of release of (125)I-labeled cell surface IgM and [(3)H]tyrosine-labeled IgM. Cell surface IgM was shed as 8S with an initial half-life of release of 5-8 h whereas [(3)H]tyrosine-labeled Ig was secreted as 19S with an initial half-life of 2-3 h. These findings suggest that two independent pathways are involved. It is suggested that small lymphocytes shed 8S IgM and plasma cells secrete 19S IgM. It was observed that lymphoid cells from axenic mice synthesize a higher proportion of IgM relative to total protein. Electron microscopic examination of splenocytes from such mice revealed a markedly higher proportion of plasma cells and a paucity of lymphoblasts compared to controls. It was suggested, therefore, that axenic mice lack a population of stimulated T cells which can induce a switch from IgM to IgG synthesis and which is capable of suppressing IgM synthesis. Lymphoid cells from axenic mice synthesize and secrete less protein that coprecipitates with antigen-antibody complexes.

Animals↗
PubMed1973

Synthesis, intracellular distribution, and secretion of immunoglobulin and H-2 antigen in muring splenocytes.

A/J spleen cells were labeled with [(3)H]leucine and at intervals thereafter were homogenized and separated into microsomes and cell sap. Ig and H-2 antigens were assayed in the cell fractions and cell supernatants using immunoprecipitation. In addition, cells labeled by enzymatic radioiodination were incubated to determine the rates of release of Ig and H-2 antigens from the surface. The results indicate that the majority of Ig and H-2 antigens remain membrane bound throughout their intracellular life. In contrast to Ig, H-2 antigens are neither secreted nor shed from the cell surface. It is suggested that Ig is a peripheral protein of the cell membrane, whereas H-2 antigens are integral ones. The release of Ig on a fragment of plasma membrane could occur at fixed cell surface areas that contain no H-2 antigens or from which they have migrated before release.

Animals↗
PubMed1973

Immunoglobulin synthesis and secretion by cells in the mouse thymus that do not bear theta antigen.

The mouse thymus contains cells that synthesize and secrete minute amounts of immunoglobulin (Ig). These cells were studied by a combination of cytotoxic tests (with alloantisera prepared in congenic strains of mice) followed by pulse labeling of the surviving cell population with [(3)H]tyrosine. The immunoglobulin-synthesizing cells constitute less than 2% of the total cell population and are theta(-), TL(-), Ly-B(-), Ig(+), H-2(+), and PC(+). Since this phenotype is not characteristic of cells of the thymocyte lineage, the Ig(+) cells are probably plasma cells and/or bone marrow-derived (B) lymphocytes. Similar studies of spleen cells indicate that immunoglobulin-synthesizing and secreting cells are theta(-).

Animals↗
PubMed1972

Cell surface immunoglobulin. V. Release from murine splenic lymphocytes.

Turnover and release of cell surface Ig and secretion of total intracellular Ig has been studied in small lymphocytes from normal mouse spleen. The major findings to emerge are: (a) small lymphocytes secrete 8S IgM and IgG. A small portion of the 8S IgM, but virtually none of the IgG appears to have a cell surface phase. (b) Cell surface IgM is actively turned over with a half-life of 6-8 hr, and turnover can be accounted for by release into the incubation medium. Release is temperature dependent. (c) Released cell surface Ig is noncovalently bound to a fragment of plasma membrane. (d) H-2 antigens are not released during short-term incubation. Based on the above findings, we propose a model for the transport and release of both cell surface and conventionally secreted Ig.

Animals↗
PubMed1972

Cell surface immunoglobulin. IV. Distribution among thymocytes, bone mrrow cells, and their derived populations.

Thymocytes, bone marrow cells, and their derived T and B cell populations were examined for the presence of Ig by the cell surface radioiodination technique. Both IgM and IgG were identified on bone marrow cells. Thymocytes and T cells had no detectable cell surface Ig. Radiolabeling of mixtures of B cells and thymocytes suggest that the method may detect as little as 250 molecules of Ig per cell. Based on these findings, we suggest that the T cell receptor for antigen is not a conventional tetrameric Ig.

Acrylamides↗
PubMed1971

Cell surface immunoglobulin. II. Isolation and characterization of immunoglobulin from mouse splenic lymphocytes.

The proteins on surfaces of living splenic lymphocytes from normal BALB/c mice were iodinated enzymatically. Such cells were fractionated into two sub-populations: one composed almost exclusively of small lymphocytes and the other mainly of large lymphocytes and plasma cells. Specific immunoprecipitation of radiolabeled surface Ig obtained from lysates of these cell populations indicated that approximately 2-3% of the acid-precipitable radioactivity from the cell surface is Ig. Moreover, 95% of the H chain radioactivity from the Ig of the small lymphocyte fraction and 90% from the large lymphocyte-plasma cell fraction was characterized as micro by precipitation with anti-micro sera as well as by molecular weight determination on polyacrylamide gels in sodium dodecyl sulfate. The Ig was recovered from the cell surface in the form of an IgM monomer. Control experiments suggested that the monomer did not result from depolymerization of 19S IgM by the methods used to radiolabel and isolate the molecule. (3)H-tyrosine labeling of IgM produced by meyloma cells and radio-iodination of IgM in solution gave the same ratios of microL radioactivity as radiolabeling of IgM on cells, indicating that the tyrosine residues of L and micro-chains of cell surface IgM are available to the lactoperoxidase during the iodination. This is consistent with the hypothesis that cell surface IgM is entirely on the outside of the plasma membrane presumably attached to it by its Fc fragment. These results, together with previous reports by others, suggest that IgM, in its monomeric form, is the main antigen-specific receptor on lymphocytes of normal mice.

Animals↗