Concentrations of proteoglycan (PG)-specific serum antibodies and percentages of spleen B cells in severe combined immunodeficient (SCID) mice treated with placebo or FTY720 after receiving complete donor lymphocyte transfer and in SCID mice receiving T cell-depleted transfer. Serum levels of (a) human PG (hPG)-specific antibodies and (b) mouse PG (mPG)-specific autoantibodies of the IgG1 isotype were determined by enzyme-linked immunosorbent assay and expressed as milligrams per milliliter and micrograms per milliliter, respectively. N.D., not detectable. (c) The proportion of B cells in the spleens of the three groups of SCID mice was measured by flow cytometry and expressed as percentage B220+ of total CD45+ cells. Data shown are the mean + standard error of the mean (n = 9 to 11 mice per group).