THE ESTABLISHING OF THE IMMUNE SYSTEM OF THE scid MOUSE BY THE TRANSPLANTATION OF THE XENOGENEIC IMMUNE STEM CELLS

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Because the lymphocyte stem cell has a malfunction, no population of both T and B cells exists in the lymphoid organs of scid (scid/scid) mouse. However the thymus is equipped with the normal organization. Therefore, when transplanting the bone-barrow cells of nude (rnu/rnu) rat to the scid mouse (rat BMT scid mouse), the lymphocytes of the donor origin immigrate into the thymus. Those lymphocytes get to express rat CD3, CD4, CD8 and TCR antigens like the normal rat thymocytes do. The T cell population of the rat origin emerged to the peripheral lymphoid organs, and B cells of rat origin which can produce immunoglobulins emerged there at the same time. These evidences show that the immune system of rat origin can grow sufficiently in the scid mouse. On the other hand, when transplanting the thymic lobes of the 15th of embryonic rats under the kidney capsule of scid mouse, the lobes grow. The immature T cell population which existed in the grafts developed there and emerges to the periphery as the functional T cells. Then, this mouse falls into GVHD after several months of the rat thymus graft and dies. At the rat BMT scid mouse, neither GVHD nor localized autoimmune diseases developed and the long-range survival is possible. We gave the rat BMT scid mouse a foreign antigen (SRBC) and examined immune function but the reaction was very weak. This phenomenon is peculiar, because both the expression patterns of TCR of T cells and IgG of B cells in rat BMT scid mouse are as those of normal rat. When injecting the spleen cells of the rat BMT scid mouse into nude rat, the decrease of the weight is remarkable from 3 months to 5 months after the treatment and the GVHD-like disease occurred. The rat BMT scid mouse is the model which is extremely useful to study education effects to the T cell of the thymus.