Table 1.

MHC based cell rejection. The table briefly summarizes the issues related to cell transplants being rejected. The MHC systems is primarily responsible for recognizing self vs non-self. However other antigens and the innate immune system also contribute to rejection

The MHC system & foreign antigens
• MHC Class I by most cells in adult Including neural stem cells.
• Embryonic cells have little or none but will express them on inflammation or differentiation
• MHC Class II by professional APC such as T cells, B cells, macrophages, endothelial cells and thymic epithelial cells
• Different HLA antigens responsible for rejection at different time points. HLA-DR mismatch important in the first 6 months, the HLA-B in the first 2 years, and HLA- A mismatches over the long-term
• Foreign antigens are presented by cells expressing Class I or II peptides on surface and lead to activation of T cells, B cells and macrophages.
• ABO blood groups and sex differences may have effects on transplants
• T–regs, Complement, atypical MHC antigens (HLA G), minor antigens and modulators of local immune response (indoleamine, NO, etc.) can exacerbate or inhibit rejection
• GVH (graft versus Host) immune issues may be important for blood derivatives