Efficiency of intrathymic tolerance induction in various inbred rat strains: relationship with T(H)1/T(H)2 status of the recipient?

The simultaneous transplantation and intrathymic tolerance induction (STITT I) protocol induces a longlasting state of functional tolerance in over 90% of AO (RT1(u)) recipients transplanted with a fully MHC-incompatible PVG ( RT1(c)) cardiac allograft. Similar results are obtained when using LEWIS (R T1(l)) rats as recipients of either PVG or DA (RT1(avl)) grafts. However, w hen STITTI is performed on PVG and BN (RT1(n)) as recipient animals receivi ng spleen cells intrathymically and a cardiac allograft from respectively A O and PVG rats, this procedure results in significantly shorter graft survi val (MST PVG --> BN 25 +/- 9 days; AO --> PVG 31 +/- 8 days) as compared to the combinations using AO (MST PVG --> AO > 236 +/- 28 days) and LEWIS (MS T PVG --> LEW > 366 +/- 51 days; DA --> LEW > 123 +/- 33 days) rats as reci pients. Since both PVG and BN rats are relatively deficient in their abilit y to produce IFN gamma and intrathymic IFN gamma responses are very dominan t upon intrathymic injection of alloantigens, it is argued that the inabili ty to effectively induce a longlasting state of functional tolerance in BN and PVG rats using the STITTI protocol may be related to their decreased IF N gamma-production potential.