The differentiation of cytotoxic T lymphocytes in vitro: an ultrastructural study

Immunoelectron microscopy of acute graft versus host disease of the skin after allogeneic bone marrow transplantation

AIMS

To clarify the pathological mechanisms of acute cutaneous graft versus host disease (GvHD) following allogeneic bone marrow transplantation.

METHODS

Skin biopsy specimens from five patients were examined by immunoelectron microscopy. A panel of monoclonal antibodies against T cell and natural killer cell subpopulations was used, including anti-CD4, -CD8, -CD16b, -CD56, -CD57, and -TCR delta 1 antibodies.

RESULTS

All the specimens contained CD8+ cells, CD4+ cells, and CD56+ cells infiltrating the epidermis. Cells stained with anti-CD16b, -CD57, or -TCR delta 1 were very sparse or absent. Most of the CD8+ cells in the epidermis displayed morphological features of activated cytotoxic T lymphocytes and apposition of such cells to degenerating keratinocytes was shown. CD4+ cells outnumbered CD8+ cells in the epidermis in all five cases. Noticeable intercellular as well as intracellular oedema of keratinocytes was observed at the site of prominent CD4+ cell infiltration, suggesting that these also have a role as actual effector cells by secreting cytotoxic cytokines. CD56+ cells infiltrating the epidermis did not exhibit the characteristic ultrastructural morphology of the natural killer cells thus far examined, and their lineage remained uncertain.

CONCLUSIONS

These data provide direct evidence that CD8+ cytotoxic T cells attack keratinocytes, and further suggest that CD4+ cells as well as CD56+ cells participate in the cellular pathogenesis of acute cutaneous GvHD.

Fibroblast cytotoxicity associated with plasma cells and lymphocytes in chronic periodontitis lesions in rats

INTERDENTAL PERIODONTITIS LESIONS in rats 20 to 27 months of age were found to contain large aggregations of plasma cells and lymphocytes. Fibroblasts in areas of dense immunocyte infiltration appeared damaged. The close juxtaposition of both plasma cells and lymphocytes to the altered fibroblasts suggests that a cytotoxic effect of immunocyte origin might be a significant element in connective tissue alteration in advanced periodontitis lesions in older rats. At the ultrastructural level, the damaged fibroblasts exhibited alteration of the nucleus, loss of cytoplasmic content including microfilaments and microtubules, swelling and degeneration of mitochondria and Golgi vesicles and cisternae. Dilation of the rough endoplasmic reticulum, including the perinuclear cisterna, along with vesiculation of the cytoplasmic membranes, suggests osmotic dysfunction in various cellular organelles.

The identification of human T and B lymphocytes by electron microscopy

Lymphocytes of peripheral blood, bone marrow, spleen, vermiform appendix, tonsil and Mantoux skin reaction were examined by electron microscopy (EM) and classified as T, B and Null cells by E-rosette and immunoglobulin membrane-receptor characteristics. The low pH and ionic strength of the fixative solution for EM, and some other minor procedural modifications, made it possible to distinguish B and T lymphocytes morphologically. T-cells have electron-dense cytoplasm and euchromatin in the nucleus whereas B-cells constantly have electron-lucent cytoplasm and euchromatin in the nucleus. A proportion of lymphocytes were unclassifiable by their ultrastructural features. These unclassifiable cells may be Null cells as determined by the classical techniques. The specificity and simplicity of this EM technique for T and B lymphocytes is especially useful for studies of immunocompetent-cell topography and cell-to-cell interaction in lymphoid organs. It may also be utilized for diagnostic purposes in immunocytic dyscrasias.