A Rabbit Antiserum to a Thymus Extract Specific for Mouse Thymus-Derived Cells

Abstract A heteroantiserum has been prepared in rabbits against an EDTA eluate of mouse thymus. The globulin fraction of the unabsorbed serum precipitates macromolecules of several molecular weights eluted from various lymphomas. It is highly cytotoxic to both Thy-1 (ϑ)-positive lymphomas and normal thymus cells, but is also cytotoxic to some bone marrow cells. After absorption with insolubilized serum proteins and bone marrow cells, the serum is highly specific for mouse thymus-derived cells. Indirect immunofluorescence of thymus cells assessed by rapid-flow fluorescent measurements gives a single sharp distribution; the activity of thymusderived cells is specifically removed from primed spleen cells by the absorbed serum plus complement when tested in an in vivo transfer system. The antiserum does not discriminate between Thy-1 (ϑ) alleles.