Monoclonal antibody to human platelet glycoprotein I. I. Immunological studies.

A monoclonal hybridoma antibody specific for platelet glycoprotein I complex is described. The nature od the antigen was determined by demonstration that it was chymotrypsin sensitive and gave a peak at 150 000 daltons on SDS-PAGE after immunoprecipitation. The expression of the antigen is restricted to platelets and megakaryocytes with at least 1.6 x 10(4) molecules of antigen per platelet. The antibody failed to bind to platelets from patients with Bernard Soulier syndrome, where there is known to be a deficiency of glycoprotein Ib/Is expression. Binding to platelets from patients with Glanzmann's thrombasthenia was normal.

Influenza virus-specific cytotoxic T lymphocytes recognize HLA-molecules. Blocking by monoclonal anti-HLA antibodies.

The effect of monoclonal anti-HLA antibodies on lysis of influenza virus-infected target cells by sensitized cytotoxic T lymphocytes was measured. Lysis was blocked, provided the antibody was present in a concentration sufficient to saturate the HLA determinants on the target cells. Antibodies to monomorphic HLA determinants and to beta 2-microglobulin inhibited. Antibody to HLA A2 and B17 blocked lysis of target cells that shared these antigens with the effector cell. It was concluded that the restriction elements for influenza virus-specific cytotoxic T cells are the HLA molecules themselves.

Subpopulations of normal and leukemic human thymocytes: an analysis with the use of monoclonal antibodies.

Combinations of antibodies to membrane antigens and to terminal deoxynucleotidyl transferase (TdT) were used to study human thymocyte and bone marrow subpopulations and leukemia cells. Cortical thymocytes were TdT+ and expressed T-cell antigens (HuTLA+), a thymocyte-specific antigen (HTA-1+), and a leukocyte antigen (HLe-l++) but lacked detectable HLA-A,B,C and la (HLA-D) antigens. In contrast, medullary thymocytes were TdT-, HuTLA+, HTA-1-, HLe-l++. A small subpopulation of larger, probably immature, thymocytes were strongly TdT+, HuTLA+, la-, HTA-1-, HLe-l +/-. Many blast cells from cases of thymic acute lymphoblastic leukemia (Thy-ALL) showed the phenotype of this small subset, and only a proportion of Thy-ALL blast cells exhibited HTA-1 and HLe-l antigens as strongly as was observed on normal cortical thymocytes. In contrast, TdT+ cells observed in normal juvenile bone marrow were HuTLA, HTA-1-, HLA+, la+. This phenotype corresponded to the phenotype of the common form of ALL (non-T, non-B) and indicated that further studies are necessary to analyze the differentiation of bone marrow precursors to thymic cells.

A human thymocyte antigen defined by a hybrid myeloma monoclonal antibody.

Spleen cells from a BALB/c mouse that had been immunized with human thymocytes were fused with the myeloma line P3-NS 1/1 Ag 4.1. One of the resulting hybrid clones (NA 1/34) secreted an antibody that was highly specific for human thymocytes. Eighty-five % of thymocytes expressed the antigen designated HTA1. There were an estimated 15 x 10(4) molecules of HTA 1 per cell, and it is therefore a major surface molecule. The expression of this antigen on thymocytes appears to be reciprocal to HLA, as recognized by another monoclonal antibody W6/32. Immunoprecipitated material from [125I]-labeled thymocyte membranes was analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate which disclosed a single component of 45,000 molecular weight.