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Graft vs. host disease (GVHD) remains one of the main problems associated with bone marrow transplantation. The current studies were undertaken to determine whether treatment of the donor inoculum with the anticytotoxic cell compound L-leucyl-L-leucine methyl ester (Leu-Leu-OMe) would alter the development of GVHD in a murine model.

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Human graft-versus-host disease (GVHD) has several cutaneous manifestations, including a lichenoid and a sclerotic injury pattern. A versatile animal model of graft-versus-host skin disease (GVHSD) would facilitate study of the pathophysiology of these two cutaneous injury patterns. We have examined two murine chimeras histologically and have found two distinct patterns. Allogeneically transplanted B1/6 mice show a prolonged lichenoid-interface dermatitis that eventuates in clinical alopecia, whereas LP/J recipients of allogeneic cells do not show hair loss. Their histopathology consists of an early lichenoid phase that abates and is replaced by dermal sclerosis. Because of the versatility of the mouse as a laboratory animal, we feel that this model provides an excellent opportunity to define the immunopathologic mechanisms responsible for skin injury in GVHD. In addition, an understanding of the pathogenesis of the T cell-dependent, lichenoid, and sclerotic patterns of tissue injury in GVHSD might well provide insight into the pathogenesis of the GVHSD analogs, cutaneous lupus erythematosus and scleroderma.

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Although mast cells have been implicated in mediating antitumor activity, the kinetics, mechanism(s), and suspectibility of different tumors to mast cell-mediated cytotoxicity have not been defined. Rat connective tissue mast cells (CTMC) of greater than or equal to 99% purity were investigated in vitro and found to express maximal spontaneous cytotoxicity against the mouse fibrosarcoma cell line WEHI-164 (56.0% +/- 2.1 SEM), the ultraviolet B (UVB)-induced, cutaneous fibrosarcoma 5C25 (34.7% +/- 3.4 SEM), and the human renal cell tumor Currie (26.8% +/- 2.0 SEM) at an effector to target (E:T) ratio of 80:1. Kinetic studies of CTMC-mediated cytotoxicity demonstrated significant detectable lysis against these tumors within 8 h, which was maximal by 16 h. Binding experiments showed that CTMC formed conjugates with all three lytic-sensitive targets; however, CTMC also attached to the lytic-resistant target YAC-1, indicating that conjugate formation alone is not sufficient for mast cell-mediated cytotoxicity. At two different concentrations, mast cell granules (MCG) lysed WEHI-164 (36.5% +/- 6.8 SEM) and 5C25 (34.4% +/- 6.9 SEM), but were only slightly cytotoxic (5.7% +/- 2.9 SEM) against Currie. A potential role for tumor necrosis factor-alpha (TNF-alpha) in CTMC-mediated cytotoxicity also was investigated. Polyclonal antibodies to TNF-alpha greatly reduced CTMC and TNF-mediated lysis of WEHI-164, but only partially inhibited CTMC killing of the slightly TNF-sensitive 5C25 tumors, and had no effect on CTMC cytolysis of Currie. Thus, this study demonstrates that CTMC mediate cytotoxicity in vitro by both TNF-associated and TNF-independent mechanisms. We conclude that CTMC are capable of mediating antitumor activity and that this effect may be important for tumor surveillance in the skin and other sites.

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