High molecular weight antigens present on human T cells

Surface Ly-5 glycoprotein in murine natural killer (NK) cell development, target binding and cytotoxicity

The role of surface Ly-5 glycoprotein expression in the binding and lysis of susceptible tumor targets by natural killer cells was studied using NK cell-enriched splenocytes from 6-8 week old C57BL/6 mice which were reacted with anti-Ly-5 serum in the presence or absence of a source of complement. A conjugate assay was used to demonstrate that abrogation of tumor cell lysis by anti-Ly-5 serum involved the inhibition of NK cell binding to susceptible YAC-1 targets. Additionally, reconstituted membrane vesicles from NK cell-enriched splenocyte populations blocked binding of effector cells to YAC-1 lymphoma targets, a phenomenon which was abrogated by pretreatment of vesicles with anti-Ly-5 serum. Indirect immunofluorescent labeling and cell sorting were used in the physical separation of Ly-5+ and Ly-5- cells to examine the effect of interferon and interleukin preparations on Ly-5 expression and Nk activity. Three hour treatment of sorted Ly-5- cells with murine alpha + beta interferon resulted in conversion of 22% of the cells to an Ly-5+ phenotype, as well as a significant increase in the percent specific lysis of NK-susceptible YAC-1 targets when compared to freshly sorted Ly-5- cells (29.5 +/- 1.9 vs 2.6 +/- 4.0; p less than .001). In vitro proliferation of sorted Ly-5- cells was induced by three week culture in an interferon- and interleukin-containing supernatant from ConA stimulated BALB/c splenocytes (CM), followed by repeat analysis of Ly-5 expression and cytotoxic activity. Cell sorter purified Ly-5- cells cultured in CM acquired substantial surface Ly-5 with concomitant high levels of cytotoxic activity that remained partially susceptible to inhibition by anti-Ly-5 serum. The data presented suggest that surface Ly-5 glycoprotein expression is important for binding of freshly isolated NK cells to YAC-1 targets. In addition, Ly-5- precursors of NK cells are present in murine splenic tissues and can be induced by CM to become highly active effector cells with increased surface Ly-5 expression. The persistent susceptibility of a subset of these cells to inhibition of cytotoxic activity by anti-Ly-5 serum provides additional evidence of an important role for the Ly-5 glycoprotein in the natural killer cell cytolytic mechanism against certain targets.

Demonstration of T200 on human Langerhans cell surface membranes

We have demonstrated the presence of the glycoprotein T200 on the surface of human epidermal Langerhans and indeterminate cells by immunoelectron microscopy with the use of a monoclonal antibody. No other epidermal cells were positive. The presence of T200 on Langerhans cells confirms their hematopoietic origin because T200 is limited to hematopoietic cells and neoplasms. Although the function of T200 is not known, antibodies directed against T200 have been previously shown to inhibit accessory cell and natural killer cell activities. While the existence of a possible relationship between Langerhans cells and natural killer cells is unclear, Langerhans cells are important in cutaneous accessory cell functions; therefore. T200 may be important in understanding the biology of Langerhans cells and their relationship to other cells in the immune response.

A common epitope identified by a monoclonal antibody, MID 2, present on all leucocytes and associated with a group of high molecular weight glycopeptides

A monoclonal antibody, MID 2, which reacts with an epitope common to all human leucocytes, was used to show that the leucocyte common antigen can be resolved into four glycoprotein components with molecular weights of 220 K, 200 K, 180 K and 160 K. The 200, 180 and 160 K peptides were all present to various extents in the T and B lymphoblastoid cell lines examined, but the 220 K component was only detected in the B-cell lines. The 220 K glycoprotein was also lacking in human thymocytes, but evidence of its expression in peripheral blood T lymphocytes was obtained, suggesting that it might be acquired as the cells differentiated. The four glycoproteins isolated from tonsil cells gave similar patterns on peptide mapping by the Cleveland enzymatic method or by cyanogen bromide cleavage, indicating extensive homology. It is conceivable that they differ from each other by the acquisition of similar repeating domain sequences of approximately 20 K. Alternatively, they may share a common peptide structure but differ in their electrophoretic behaviour in SDS gels owing to differences in carbohydrate; if this is the case, however, experiments with tunicamycin suggest that O-linked oligosaccharides must be involved.

Partial isolation and characterization of Gp 220, the Ulex europaeus binding glycoprotein of the B-lymphocyte plasma membrane

Using affinity chromatography on Sepharose 4B coupled with Ulex europaeus lectin, a partially purified gp 220 was isolated from the RAJI cell membrane. This protein could not be isolated from the membranes of the T-cell line MOLT-4 nor from human erythrocytes. Gp 220 is composed of three subunits gp 85, 70 and 65 held together by disulfide bridges. Gp 85 contains fucosyl residues, gp 70 contains galactosyl residues, and gp 65 contains both sugars. Gp 220 is different from fibronectin and spectrin, proteins which also show binding to the Ulex europaeus lectin.

Analysis of human T-cell antigens by one- and two-dimensional polyacrylamide gel electrophoresis

One- and two-dimensional polyacrylamide gel electrophoresis (PAGE) was performed on immunoprecipitates formed between anti-human T-cell xeno-antiserum (ATS) and cell-surface glycoproteins of human lymphocytes, that had been radioiodinated by lactoperoxidase and purified on a Lentil lectin-coupled Sepharose 4B column. In some experiments, the cells were 3H-labeled by periodate-tritiated borohydride. ATS that was absorbed with B cells recognized a number of cell-surface antigens expressed preferentially on human thymus and T cells, with molecular weights of 150K (T150), 94K (T94), 72K (T72), and 65K (T65) daltons. Whereas T150 appeared to consist of multiple components of heavily sialylated glycoproteins and to be expressed largely on thymus and T cells, and to a much lesser extent on B cells, the remaining T94, T72, and T65 glycoproteins seemed to be present on thymus and T cells but absent from B cells. Two-dimensional PAGE analysis of these T-cell glycoproteins precipitated by ATS demonstrated that T94 was an acidic glycoprotein with pI of 4, while T72 and T65, the latter being found on thymus and T cells but not on T cell-type leukemic cells, exhibited marked electric charge heterogeneity with pI ranging from 4 to 7. These data clearly suggest that human thymus and T cells possess a complex antigenic make-up on their cell surfaces, comparable to that of mouse T cells with a variety of Ly antigen systems.

Human T cell surface antigens bearing a structural relationship to HLA antigens

Three cell surface antigens that are structurally related to the human major histocompatibility antigens (called HLA antigens) have been characterized from the leukemic T cell line MOLT-4. One antigen is a glycoprotein of Mr 49,000 recognized by two monoclonal antibodies. OKT6 and NA1/34, and is associated with a Mr 12,000 subunit that crossreacts serologically with beta 2-microglobulin but can be distinguished from it by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. A second antigen, defined by the monoclonal antibody OKT10, is a Mr 46,000 protein associated with a small subunit distinct from beta 2-microglobulin. The OKT10 antigen is not restricted to T cells and is found on all T and B lymphoblastoid cell lines tested. The third protein is a beta 2-microglobulin-associated glycoprotein of Mr 43,000 that is serologically distinct from the OKT6 (NA1/34), OKT10, and HLA antigens. It is found on some, but not all, T cell lines but is absent from any other hematopoietic cell lines tested.

Dissection of distinct human immunoregulatory T-cell subsets by a monoclonal antibody recognizing a cell surface antigen with wide tissue distribution

A monoclonal antibody, PVR-11, was obtained after hybridization of X63Ag8.653 murine myeloma cells with spleen cells from a mouse immunized with human lymphocytes. It recognizes a 175,000- to 185,000-dalton surface antigen present on approximately 80% of normal human peripheral T lymphocytes, 50% of non-T non-B cells, and less than 10% of B cells as determined by complement-dependent microcytotoxicity. It is also present on various leukemia T cells, on some but not all T lymphoblastoid cell lines, and on a small fraction of some B lymphoblastoid cell lines. Some B-cell chronic lymphocytic leukemia cells also express the PVR-11 antigen. Functional analysis of normal human T lymphocytes demonstrated that the PVR-11-depleted T-cell subset contains the precursors of both cytotoxic and suppressor cells but lacks helper cells. On the other hand, cytotoxic effector T cells express the PVR-11 antigen. These results demonstrate that antigenic determinants with relatively wide tissue distribution can dissect functionally distinct human immunoregulatory T-cell subsets.