Kinetics of donor cell infiltration of (A) liver and (B) spleen in the GVL (□) or GVH (▪) system. Frozen tissue sections were stained for donor cells with anti-β₂M^b immune complexes and analyzed under the microscope. The data indicate the means and standard deviations (SD) from five separate experiments with 5 to 8 animals per time point. Points without SD indicate values for which the SD was smaller than 1.