Abstract
The identification of T lymphocyte subsets by means of monoclonal antisera in tissue has so far been restricted to light microscopic observations on cryostat sections, since the conventional fixatives as formaldehyde, B5, or glutaraldehyde seem to denature the surface antigens. Applying a mild fixative, periodate-lysine-paraformaldehyde (PLP), we were able to demonstrate T cell subsets on the electron microscopic level in human tonsils with minimal loss of antigenicity of the surface markers Leu 1, OKT4, OKT8, and HLA DR. The preservation of the tissue could be compared favorably to fixation with glutaraldehyde, and provided an ultrastructural basis to distinguish helper and suppressor cells by morphological features as well.