A Study On Chemical Modification Of Doner H-2 Antigen In Haploidentical BMT In A Murine Model

Background: HLA haploidentical bone marrow is a potential source of doner for children for its availability. The drawback doing so is deleterious GVHD reaction post transplantation due to the incompatibility of HLA antigen expression between doner and recipient, in which donor T lymphocytes is stimulated for proliferation and differentiation. The methoxy polyethylene glycol (mPEG) is a kind of amphoteric compound having no immunogenicity, which was used to modify various proteins covalently and to prepare versatile blood type. If mPEG modification blocks the activation of T cells in grafts, GVHD reaction probably becomes less serious and transplantation may become successful. Our aim is to use mPEG to modify the grafts with appropriate concentration, and to see if mPEG modification to H-2 antigen improves haploidentical bone marrow transplantation(BMT) in a murine model.Methods: First, the mPEG was used to modify the canine lymphocytes, and subsequently the surface antigens of lymphocytes modified by different concentrations and at different time were detected by Flow Cytometer. Then male BALB/c mice were chosen as doners, and female CB6F1 mice as recipients. There were three groups of mPEG modification, non-modification and irradiation control. The modified and non-modified mixture of bonemarrow and spleen cells were transplanted to haploidentical lethally irradiated CE6F1 mice via tail vein. After transplant, hematopoietic recovery, survival rate, acute graft versus host disease (aGVHD) and chromosomal karyotype were studied and compared with controls.Results: 1. Flow Cytometer revealed the expression of the surface antigens of lymphocytes decreased gradually with the dose increase of mPEG, and there is no association with time changes. 2. Six out of ten (60%)of mice were survived in group of mPEG modification, while only four out of ten (40%)survived in group without modification. And 100% mice died in group of irradiation control within 2 weeks. Histopathological examination of skin, liver and intestine showed typical signs of aGVHD, but the GVHD grading in group of modification were less severe. The recipient mice in both groups survived on +75 days showed complete doner-type implantation by chimerism examination.Conclusion: 1. mPEG significantly and durably blocks the surface antigens expression in lymphocytes. 2. The modification by mPEG to grafts can alleviate aGVHD and improve the survival of mice after haploidentical bone marrow transplantation.