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Synovial tissue is a highly specialized tissue that keeps the articular joint well lubricated, and at the same time provides nutrients to the articular surface. A joint needs a small amount of synovial fluid to work. Although the tissue structure is simple, its function is highly sophisticated. Because synovial tissue is the target of most autoimmune diseases, joints need to be understood in their entirety to create new treatments for such immunological disorders.

Natural killer (NK) cells from nonimmunized mice capable of lysing EL-4 (C57BL/6 strain H-2b) tissue culture-adapted lymphoma cells have been analyzed and compared with NK cells which lyse YAC-1 (A-strain, H-2a) lymphoma cells. A correlation was seen in the ability of inbred and B6D2F1 mice to reject C57BL/6 (B6) bone-marrow grafts and the ability of their spleen cells to lyse EL-4 cells in vitro. This suggests that hybrid or hemopoietic histocompatibility antigens, (Hh-1b), relevant in the rejection of B6 stem cells may also be the relevant target structures for the anti-EL-4 NK cells. Certain features of these NK cells are similar to the NK cells reactive against YAC-1 cells. Both types of NK cells are present in athymic nude mice, are not affected by treatment with anti-immunoglobulin plus complement, and are not depleted by techniques that remove macrophages. NK activity against both targets is stimulated 3 d after injection of Corynebacterium parvum, and 24 h after challenge with polyinosinic:polycytidylic acid. Hydrocortisone acetate and cyclophosphamide lead to reduction of NK activity within 2-3 d after administration. However, the anti-YAC and anti-EL-4 NK reactivities differed in several important respects. Treatment of mice with 89Sr, the bone-seeking isotope, to deplete marrow-dependent cells, depleted the anti-YAC-1 but not anti-EL-4 cell functions. Anti-EL-4 NK cells were unaffected by silica particles in vivo or in vitro; the NK cells reactive to EL-4 cells matured functionally much earlier in life (5 d of age) and the function did not decline with age. Irradiated mice reconstituted with syngeneic marrow or spleen cells developed functional NK cells against EL-4 targets before they developed anti-YAC-1 NK cells in their spleen. Thus anti-EL-4 NK cells that express hybrid resistance in vitro appear to differ from anti-YAC-1 NK cells and do not require an intact marrow microenvironment for functional differentiation. Despite differences in the NK-cell types involved in the lysis of YAC-1 and EL-4 cells, these two tumor cells share certain common determinants. This was ascertained both by cold competition and by utilization of YAC-1 and EL-4 cell monolayers as immunoadsorbents. We conclude that Hh-1b is the common antigen present in EL-4 and YAC-1 cells, because B6D2F1 anti-B6 (anti-Hh-1b) cytotoxic T lymphocytes lysed both the tumor cells. Our data suggest that Hh-1b antigen is recognized by both types of NK cells, but that additional determinants must be present on YAC-1 cells. Two models of NK cell lysis compatible with the data are presented.

A case of glial tissue in a polypoid structure of the uterine cervix is presented; the presence of glial fibrillary acidic protein was demonstrated by immunoperoxidase, confirming the astrocytic nature of the tissue. The main hypotheses to explain this unusual finding are discussed.