Immunofluorescence and elution studies in tetraparental NZB forms and is formed from CFW chimaeras and graft-versus-host diseased NZB.

Earlier evidence in these chimaeras suggested an acute interaction between the two parental strains in all of four ovum fusion-derived tetraparental NZB↔CFW chimaeras. In spite of this acute interaction indirect immunofluorescence upon unfixed tissue sections has here confirmed the presence of both H-2 defined parental strain cell populations in each mouse. This supports our earlier view that the acute reaction resulted from two separate events, and the evidence suggests that these events are the opposite of those in NZB injected with CFW spleen cells. In these graft-versus-host (GVH) diseased mice two separate events occurred. Firstly a reaction of the CFW spleen cells against histocompatibility antigens of the NZB, secondly the response of NZB host against the donor cells ( NZB—anti-CFW). In the chimaeras the primary reaction involved NZB autoantibody activity against the corresponding target. This was initiated and followed by a secondary CFW—anti-NZB response. This sequence of receptor→ determinant reactions is held responsible for the acute allogeneic activity in these chimaeras. Marked erythrophagocytosis was seen in all of the NZB↔CFW chimaeras. Immunofluorescence has revealed immunoglobulin, both allotypes, complement (MuB1) and H-2 antigens in similar cells with red cell-like inclusions. Evidence suggests that erythrophagocytosis in this situation is perhaps also dependent and initiated by the same receptor→determinant reaction. This in turn argues the presence of the corresponding receptors upon the phagocytic macrophages.