Study of the antigenic constituents of sera from mouse/rat chimaeras.

The serums of CBA mice lethally irradiated (1000 r whole-body x irradiation) and restored with rat bone marrow or fetal liver were examined by immunoelectrophoresis at various times after irradiation. Several specific rat proteins including gamma globulin, at least 2 alpha /sub 2/-globulins, 1 or 2 BETA /sub 1/-globulins, and 1 BETA /sub 2/-globulin were found. A large number of specific mouse proteins were also present, but no mouse gamma -globulins were detected. The rat constituents appear progressively and persist for long periods, indicating that they are synthesized by rat cells. There is a close correlation between the presence of rat gamma -globulin in the serum and the presence of dividing rat cells in the bone marrow and spleen. The fact that gamma -globulin is solely of rat specificity does not necessarily rule out the possibility of immune activity by the host against the graft. Several of the normal serum proteins, in addition to the gamma -globulins, originate from the injected cells, and are therefore presumably not synthesized by the liver. In chimeras grafted with rat skin, the number of specific rat serum proteins is often larger than in chimeras that have not been grafted. There was no evidence thatmore » gamma -globulins of mouse specificity were being synthesized in the chimeras although they might be present in amounts below the sensitivity of the method. Presumably, mouse cells capable of synthesizing gamma globulins were totally destroyed by irradiation. (H.H.D.)« less