Inhibition of the graft-versus-host reaction: III. altered in yxvo distribution of spleen cells pretreated with fab fragments of antithymocyte globulin¹

₅₁Cr-labeled parental strain spleen cells were pretreated in vitro with antithymocyte globulin (ATG) or Fab fragments of ATG before i.v. injection into Fi recipients. Recipients were killed at various intervals after injection and their organs were assayed for radioactivity in order to determine the in vivo distribution pattern of pretreated cells. 51Cr spleen cells pretreated with ATG were almost totally prevented from migrating to spleens, lymph nodes, bone marrow, Peyer’s patches, lungs, and peripheral blood of recipients. Pretreatment of 51Cr spleen cells with noncytotoxic Fab of ATG also inhibited localization to these organs and tissues; however, the inhibition was not as complete as that of ATG-treated cells. Localization of Fab-treated 51Cr spleen cells to recipient nodes was inhibited to a greater extent than was localization to recipient spleens. There was no significant difference in the extent of inhibition of ATG-treated 51Cr spleen cells to recipient nodes and spleen. Organ counts from recipients killed at various intervals after injection of Fab-treated 51Cr spleen cells showed that Fab- treated cells do not recover their recirculating potential in vivo.