Flow cytometric analysis of peripheral blood lymphocyte subset light scatter characteristics as a means of monitoring the development of rat small bowel allograft rejection

SUMMARY Thisinvestigation usedflow cytometry tomonitor peripheral bloodlymphocyte morphology after ratsmallboweltransplantation. Preliminary studies demonstrated thatinvitroactivated peripheral bloodlymphocytes exhibited increased cell size andgranularity as measured byflow cytometric analysis offorward (FSc) andside (SSc) light scatter characteristics. Theformation of distinct 'activated' light scatter regions bysuchlymphoblastoid transformation occurred concomitantly withup-regulated p55IL-2R expression. Heterotopic small boweltransplantation was performed between PVG donorandDA recipient ratswithout immunosuppression. Animals receiving isografts served ascontrols. Peripheral bloodlymphocyte subsets were identified using appropriate MoAbs,andthelight scatter characteristics ofeachcell subset were determined by backgating strategies. Increased proportions ofactivated a/:l Tcell receptor (TCR)-positive cells could bedetected inallografted animals asearly asday2post-transplantation. Bcells showed peak activation byday4,atwhichtimetheproportion ofactivated cells was overtwo-fold greater than that seeninuntransplanted animalsfewactivated Bcells were detected inisografted animals. Resting natural killer (NK)cell light scatter regions onlypartially overlap withthose ofresting T andB lymphocytes, butinallografted animals almost theentire NK population fell outside the resting lymphocyte gatebyday2post-transplantation, an activation state which was maintained until day4.Thesefindings associate peripheral bloodcell subset lymphoblastoid transformation withdeveloping small bowelallograft rejection. Importantly, changes were detected early and prior totheonsetofovertrejection. Thesedatasuggest thatanalysis ofperipheral blood lymphocyte light scatter properties may provide an insight intoinvivoimmunestatus after small boweltransplantation.