The Major Histocompatibility Complex (MHC) of the Secondary Transplant Tissue Donor Influences the Cross-Reactivity of Alloreactive Memory Cells

Abstract

Memory cells are currently thought to be a major barrier to tolerance induction in transplantation. However, whether alloreactive memory cells resulting from a primary transplant have cross-reactivity in a second transplant is unclear. Here, we used skin transplantation from BALB/c mice donors to presensitize C₅₇ BL/6 (B6) mice. One month later, several strains of mice (including BALB/c, DBA/2, NOD, C3H and B6 mice) were chosen as donors to construct a memory model of heterotopic cardiac transplantation. The higher degree of major histocompatibility complex (MHC) mismatch to sensitizing MHC resulted in longer median survival times (MSTs, BALB/c 3.63 days versus C3H 6.08 days). After 3.5 days of cardiac transplantation, compared with the BALB/c and DBA/2 groups, in the groups of NOD and C3H, the infiltration of inflammatory cells in the grafts, the proportion and proliferation of memory cells in spleens and the function of allogeneic antibodies decreased significantly. The varying degrees of MHC mismatch between the primary and secondary donors influenced the intensity of alloreactive memory cell function, the higher degree of MHC mismatch resulted in better tolerance during secondary transplantation, and these may be related to the changed activation, proliferation and function of the alloreactive memory cells.