We have shown previously that high levels of IFN-beta were generated in vitro from spleen cells obtained from mice experiencing graft vs host disease (GVHD). However, very little or no IFN-gamma was found in these cultures even when IL-2 or Con A was added as a stimulant of IFN-gamma production. This study was undertaken to determine if the IFNs were similarly produced in vivo during the GVH reaction and to further explore the inability of GVHD spleen cells to produce IFN-gamma in vitro. GVHD was induced across minor histocompatibilities by the i.v. injection of B10.D2 spleen cells into sub-lethally irradiated BALB/c mice. Using cytoplasmic immunofluorescence to detect IFN-beta and -gamma, both IFNs were readily detectable in vivo in spleens of mice undergoing GVHD. IFN-gamma demonstrated a distinct distribution pattern, localizing in the peri-arteriolar lymphoid regions of the spleen, whereas IFN-beta immunofluorescence appeared diffusely in all areas. Expression of both IFN-beta and -gamma was shown to be dependent on the GVH reaction, inasmuch as syngeneic controls and mice given T cell-depleted donor cells had little immunofluorescence. These results contradict in vitro data in that IFN-gamma cannot be found in GVHD spleen cell cultures even in the presence of Con A. This in vitro unresponsiveness appeared to be due to the mixing of different cell populations as a result of preparing splenic single-cell suspensions. Percoll gradient fractionation of GVH spleen cells yielded a cell population which, when stimulated with Con A, produced IFN-gamma and underwent cell proliferation. This study represents the first description of the in vivo splenic distributions of IFN-beta and -gamma during GVHD, and presents data that suggest that in vitro results may not truly reflect in vivo immune responsiveness. Thus, the IFNs may play a critical role in the complex events leading to the GVHD syndrome.
We have previously shown that both IFN-gamma and IFN-beta are produced in vivo and in vitro by spleen cells obtained from mice experiencing a chronic form of graft vs host disease (GVHD). Further, we have shown that in vitro production of IFN-beta by spleen cells from GVHD mice may play a role in the suppressed in vitro mitogen responsiveness of these cells. This study was undertaken to investigate if treatment of such mice with mAb to IFN-gamma or IFN-beta could alter the immunosuppression or lymphoid hypoplasia associated with chronic GVHD. GVHD was induced across minor histocompatibilities by the i.v. injection of B10.D2 spleen cells into sublethally irradiated BALB/c mice. These mice were given daily injections for 20 days of one of the following: 1) mAb to IFN-gamma, 2) mAb to IFN-beta, or 3) control IgG. Histologic examination of these mice at 21 to 22 days post transplantation revealed that mice treated with mAb to IFN-beta or control IgG had dramatic hypoplasia of the thymus, spleen, and lymph nodes which was similar to untreated GVHD mice. Mice given mAb to IFN-gamma, however, had no lymphoid hypoplasia and had a near normal gross and histologic appearance of their thymus, spleen, and lymph node tissue when compared with syngeneic controls. In vitro mitogen-induced proliferative responses of spleen and lymph node cells obtained from GVHD mice or GVHD mice treated with mAb to IFN-beta were severely suppressed or absent. In contrast, spleen and lymph node cells from GVHD mice given mAb to IFN-gamma were capable of giving a significant in vitro proliferative response to Con A, PHA, and LPS. Further, natural suppressor cell activity and spontaneous production of IFN-beta, a characteristic of this form of GVHD, was absent in spleen cells obtained from GVHD mice treated with mAb to IFN-gamma. These results further identify the IFN as playing critical roles in the pathogenesis of GVHD.
Histologic examination of kidneys from rats infected with the hemosporidian protozoan Babesia rodhaini demonstrates the presence of a moderate, acute proliferative glomerulitis. Immunofluorescent studies establish that this renal complication is associated with glomerular deposits of IgG and the third component of complement (C3) in a pattern that is diagnostic for soluble, immune complex-induced nephritis. Acid elution of proteins from involved kidneys leads to the recovery of IgG that is reactive with babesial antigen. In the course of rat babesiosis hypocomplementemia develops, coincident with the parasitemia, severe anemia and glomerular deposits of IgG and C3.
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