Cell type-specific neural cell surface antigens.

Immunological methods have served to define several cell surface antigens that are differentially expressed among neural cell types and are developmentally regulated. These antigens have served as useful markers for cell identification and isolation of several neural cell types. The molecular nature and functional properties of almost all of these antigens are presently unknown.     

Specific cell-induced transformation of Paramecium surface antigens.

Paramecia may induce in other paramecia specific changes in the expression of genes determining surface protein synthesis, probably via cell-to-cell contact. Transformation from one antigenic type to a newly induced one is stimulated by the pretreatment of a cell with 5-fluorouracil. These observations are considered in terms of the regulation of the activity of genes in stable cells and in unstable cells which tend to transform spontaneously.     

Changes in surface antigens on preimplantation mouse embryos.

Changes in the expression of specific cell surface antigens on preimplantation mouse embryos were examined by immunocytochemistry. Embryos were recovered at various times during the preimplantation phase of normal pregnancy, and from pregnancies with experimentally induced delayed implantation, and were probed with a panel of monoclonal antibodies against murine leukocyte antigens. Antibodies directed against certain macrophage surface glycoproteins (i.e., Mac-2 and Mac-3) and those against lysosome-associated membrane glycoproteins (i.e., LAMP-1 and LAMP-2) reacted specifically with cell surface determinants on the embryos. Differences in the spatiotemporal patterns of antibody binding during normal and delayed implantation indicate that expression of the antigenic determinants recognized by these antibodies is regulated individually in response to intrinsic as well as extrinsic signals at the time of implantation, and thus they may be important for the process of embryo implantation.     

Soluble surface antigens of virulent Sh. sonnei]

The authors conducted an immunochemical analysis of the surface soluble antigen preparations (SSAP) obtained by extraction with physiological saline of the virulent Sh. sonnei microbes killed with acetone. Immunochemical studies by the immunoelectrophoresis and immunodiffusion methods in agar gel, separation on sepharose 4B and in polyacrylamide gel showed the presence of 3 groups of the antigens in the SSAP composition: 1) protein antigens, determining the commonness with the Sonne microbes of the II phase and intergenera associations with typhoid and enteropathogenic E. coli; 2) specific somatic antigen of the Boiven type present in small amounts in the SSAP; 3) specific antigens differing by specificity from the Boiven antigen detected in the microbes of the I phase only and possibly playing a role in the virulent and immunogenic properties of the causative agent.     

Novel cell surface antigens expressed on mouse alveolar macrophages.

Two new cell surface antigens expressed on mouse alveolar macrophages were defined by rat monoclonal antibodies. One marker, AVM-1, was detected on mouse alveolar macrophages, but it was undetectable on resident peritoneal cells, thioglycollate medium-induced peritoneal cells, and splenic macrophages. Splenic lymphocytes, thymocytes and bone marrow cells were also AVM-1 negative. Anti-AVM-1 monoclonal antibody immunoprecipitated a single polypeptide with a molecular weight of 200,000. Of particular interest was the finding that the anti-AVM-1 antibody could inhibit the formation of EA and EAC rosette on macrophage line cells. A second antigen (AVM-2) was also present on alveolar macrophages, and its molecular weight was 38,000.     

Short communications. The effect of trypsin on cell surface antigens.

The effect of trypsin on cell surface antigenic determinants was measured in a mouse plasmacytoma model. While loss of some antigenic determinants could be detected within 1 min, relevant residual antigens remained even after 1 hr. For solid plasmacytoma of such mice, trypsin could be safely used to prepare single-cell suspensions for similar studies.     

Recombinant retroviruses encoding cell surface antigens as selectable markers.

Recombinant retroviruses are frequently used in the transfer and analysis of genes. This report describes new retrovirus vectors that incorporate a cDNA copy of a cell surface antigen to function as a selectable marker. By using techniques based on quantitative cell surface immunofluorescence, these vectors allow the rapid detection and isolation of infected cells. These vectors also allow the rapid detection of packaging cell lines producing large amounts of recombinant retroviruses. Potential applications of these vectors are demonstrated.     

Presence of T cell-associated surface antigens on murine NK cells.

The expression of T cell-associated surface antigens on natural killer (NK) spleen cells of C57BL/6 mice was evaluated by cytotoxic depletion experiments with alloantisera prepared against the Thy 1, Ly 1, Ly 2, Ly 5, Ly 6, and NK 1 antigens. The NK activity of these nonimmunized spleen cells for YAC-1 leukemia cells was dramatically reduced by antisera to the Ly 5 and NK 1 antigens. Variable results were obtained with anti-Ly 6 sera--certain pools of this antiserum decreased the NK activity, whereas other pools showed only negligible effects. The NK activity of the same cell suspensions was not affected by antisera to the Thy 1, Ly 1, and Ly 2 antigens. In parallel tests the T cell-associated cell surface antigens of alloimmune T killer cells were similarly evaluated by cytotoxic depletion experiments. In this case, the activity of these cells was consistently diminished by antisera to the Thy 1, Ly 2, Ly 5, and Ly 6 antigens, but not by antisera to the Ly 1 and NK 1 antigens. On this basis it was concluded that the NK cells expressed a restricted subset of T cell-associated alloantigens and therefore may have been derived from the T cell lineage of lymphocytes.     

Interactions of vesicular stomatitis virus with murine cell surface antigens.

The process of maturation of vesicular stomatitis virus (VSV) results in the loss of 70% of the H-2k antigenic activity from L-cell plasma membranes. This phenomenon is also demonstrated during VSV infection of cells of the H-2d haplotype. Using the method of inhibition of immune cytolysis, VSV-infected L5178Y tissue culture cells and VSV-infected METH A fibrosarcoma cells grown in vivo show a loss of H-2d activity of 73 and 76%, respectively. Using monospecific antisera, it is seen that VSV infection results in a significant loss of antigenic activity of the gene products of both the H-2D and H-2K regions in cells of the H-2d and H-2k haplotypes. In hybrid cells expressing H-2k as well as H-2b, VSV infection results in the decrease of both H-2 antigenic activities to the same extent. VSV purified from L cells shows considerable H-2k activity, but the reaction of this virus with anti-H-2k serum does not prevent a normal subsequent infection with this virus. VSV may associate with H-2 antigen in the culture medium, but the results of mixing VSV with uninfected H-2-containing homogenates suggest that this association occurs only when the host cell and the cell homogenate share the same H-2 haplotype. Velocity sedimentation of VSV, which would remove contaminating cellular membrane fragments, does not separate H-2 activity from VSV. H-2 activity is also stably associated with VSV throughout sequential sucrose gradient centrifugation steps. It is possible that H-2 antigen is a structural component of VSV grown in murine cells.     

T-independent but not T-dependent antigens maintain surface Ig of lymphocytes.

The effect of T-independent (TIA) and T-dependent (IDA) antigens on the surface Ig of 24-hr cultured rabbit spleen cells was investigated by two techniques: the proportion of cells bearing surface Ig was determined by direct rosette formation with anti-light chain allotype-coated erythrocytes; the total amount of surface Ig was estimated by labeling the cells with anti-allotype ¹²⁵I-labeled Fab fragments. The addition of TIA resulted in the maintenance of the proportion of Ig-bearing cells almost to the initial level, an effect which could not be obtained with any of the TDA tested. The same type of effect was observed when the total amount of surface Ig was measured, i.e., there was a slight reduction (about 24%) in the amount of surface Ig in cultures to which TIAs were added and an almost sixfold reduction (about 70%) in cultures to which TDA, Con A, or no antigen was added. Some but not all of the TIA were able to induce [³H]TdR incorporation in 3-day spleen-cell cultures. We concluded that the common feature of TIA is the ability to stimulate the turnover of B-cell surface Ig, a feature that can be used for an easy screening of TIA.     

Cell surface antigens. IV. Immunological coorespondence between glycophorin and the a1 human cell surface antigen.

A stable human-Chinese hamster ovary cell hybrid has been produced which, in addition to the complement of Chinese hamster ovary (CHO-K1) chromosomes, contains only one human chromosome, No. 11. The human cell-surface antigens whose expression is controlled by human chromosome 11, and are expressed by this hybrid, have been defined as the AL immunogenetic complex. Although one component of this immunogenetic complex (a1) is also expressed by human red blood cells, a second component (a2) is not. Killing of an a1+ hybrid by anti-a1 serum and complement can be completely inhibited by glycophorin, the major glycoprotein component of the human erythrocyte membrane. In the presence of complement, antiserum prepared against glycophorin will kill only those cells which express a1. The anti-a1 killing activity of the anti-glycophorin can be absorbed out only by those cells which express a1. Therefore, it is concluded that the a1 cell-surface antigen has at least one antigenic component in common with glycophorin.