muramidase and Thymoma

Thymic ID cells are involved in the differentiation of mature T cells which are resistant against apoptosis. TRX/ADF is a potent thiol-related reducing agent, acts as a redox regulator, and it can attenuate the induction of apoptosis of T lineage lymphocytes. In the present study, 42 thymoma-free thymus and 40 thymoma samples were examined to identify the expression of TRX/ADF in human thymic tissue. TRX/ADF high-producer (TRXh) cells with cytoplasmic protrusions were found distributed in the thymic medulla. These TRXh cells were negative for CD3, a lymphocyte marker, keratin, an epithelial cell marker, and CD68 or lysozyme, macrophage/monocyte markers, but were positive for S100 protein and HLA-DR complex. Our results revealed that the TRXh cells in the thymic medulla were ID cells. As TRX/ADF has an important and fundamental role in cellular responses acting against oxidative stress, TRX/ADF may provide an explanation of cellular interaction between the medullary ID cells and the mature T cells.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Antigens, CD; Antigens, Differentiation, Myelomonocytic; CD3 Complex; Cell Differentiation; Child; Cytokines; HLA-DR Antigens; Humans; Immunohistochemistry; Keratins; Middle Aged; Muramidase; Neoplasm Proteins; Oxidative Stress; S100 Proteins; Thioredoxins; Thymoma; Thymus Gland; Thymus Neoplasms

The in vitro characteristics of spontaneous thymomas from BUF/Mna rats, a strain with a high incidence of these tumors, were studied. In primary cultures, the adherent cells consisted of mononuclear macrophages, mono- and multi-nuclear epithelial cells and some fibroblastic cells on day 3. The macrophages rapidly increased in number with the formation of large multinuclear cells by day 9. A modest increase in the number and nuclearity of macrophages was also noted in adherent cultures of normal thymuses from 5-week-old BUF/Mna rats. On the other hand, in cultures of thymic cells from 1-year-old or 5-week-old ACI/NMs rats, a normal control rat strain, macrophages did not increase in number and only rarely formed multinuclear cells in adherent cell cultures. These results suggest that abnormal proliferation signal(s) to thymic macrophages and/or their progenitor cells accompanies and may be involved in the development of thymomas in BUF/Mna rats.

Topics: Animals; Cell Fusion; Cell Transformation, Neoplastic; Cells, Cultured; Immunohistochemistry; Macrophages; Male; Muramidase; Rats; Rats, Inbred ACI; Rats, Inbred BUF; Thymoma; Thymus Gland; Thymus Neoplasms; Tumor Cells, Cultured