A novel 26 kilodalton antigen expressed on the surface membrane of activated T cells

We have identified and characterized the tissue distribution of the antigen recognized by a novel monoclonal antibody (mAb) 1B10, raised against an ac tivated gamma delta T cell clone. Immunohistochemistry of tissue sections, and analysis of single cell suspensions by flow cytometry revealed that mAb 1B10 weakly reacted with <6% of normal human peripheral blood mononuclear cells (PBMC). After 5-6 days of in vitro culture of PBMC activated with phy tohemagglutinin (PHA), 55% of the CD4(+) and 25% of the CD8(+) T cells beca me 1B10(+). 1B10 expression was maintained on long term cultured interleuki n 2 (IL-2)-dependent T cell receptor (TCR). alpha beta and gamma delta(+) c lones, and importantly, in contrast to resting T cells, the majority of in vivo activated synovial T lymphocytes from a patient with rheumatoid arthri tis were 1B10(+). In addition, myelo-monocytic U927 cells, tissue macrophag es and some epithelia and fibroblasts were found to react with mAb 1B10. So dium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of molec ules immune-precipitated by mAb 1B10 from radio-iodinated cell surface memb rane lysates of T lymphocyte and U937 cells revealed 26 and 29 kiloDalton ( kDa) glycoproteins respectively. In conclusion, mAb 1B10 recognizes a novel <<late>> appearing 26 kDa T cell activation antigen that may be useful for further studies of activated T cells in health and disease.