| Introduction:Xenotransplantation is the best way to solve the problem of donor absence,but its development is barrelled by the xenograft rejection. This study was designed to investigate the effect of T cells on the delayed xenograft rejection by intrathymic injection of xenogeneic antigen in the discordant cardiac xenotransplantation,and to investigate the possiblity of inducing the tolerance to cardiac xenografts by the way of T cells. Materials and methods:In this experiment,guinea-pig and SD rat were,respectively,selected as donor and recipient. Experimental animals were divided randomly into two groups: heart xenotransplantaion group and intraperitoneal injection group . In heart xenotransplantaion group,recipients were subdivided into four groups:1. the blank group(group O):recipients didn't acceptany pretreatments but heart xenotransplantation ; 2. the control group(group A):recipients were treated with CVF (0.4mg/kg) on 20-24hour before transplantation, and 0.4mg/kg at 24h intervals after transplantation until the graft rejection;3.Whole body irradiation(WBI) group(group B):recipients received 3.5 Gy(60Co) WBI on the seventeenth day (d-17) before transplantation(dO), the other pretreatments were the same as group A;4.1rradiation andintrathymic injection group(group C):the rats were pretreated by the intrathymic injection of guinea pig spleen cells( 5106 ) in the third day(d-14) after recipients had acceped single WBI,the other pretreatments were the same as group B. In order to observe the survival time of cardiac xenografts,8 rats in group O and 5 rats in every other groups were taken the heterotopic heart xenotransplantation in abdomen. The changes of peripheral lymphocytes were continuously detected in the third day,the seventh day,the tenth day,and the fourth day after irradiation in the irradiated rats. The changes of subgroup of lymphocytes were detected with the flow cytometry. The mixed lymphocyte reaction with [H3] thymidine for 24hr before harvesting was used to inspect the changes of lymphocyte function on d-17 and dO after irradiation and intrathymic injection. The flow cytometry was used to check the expression of the MHC-n antigen of guinea-pig on rat's thymus cells. In intraperitoneal injection group ,donors and recipients were divided into three groups(group a b and c),and 5 rats were peritonealy injected guinea-pig spleen cells ( 5x106 )in each group instead of heart transplantation on dO. The changes of the natural antibody (IgM and IgG ) were detectd after one week. The other management was respectively as same as group AN B and C.Results:In heart xenotransplantaion group :1. Survival time of donor heart in group B(31.2 +5.08h) ,group C(32.3 +3.38h) and group A(24.1 +5.81h) was significantly longer than group O(0.34+ O.llh) (P<0.01),group B and group C was longer than group A (P<0.05),but there was no evident difference between group B and group C(P>0.05). 2. The number of lymphocytes were descented to the lowest (20.02 + 2.31 x 109) in the third day after the whole body irradiation,then began to rise graduately,and it rised to the 68.63% (13.74+3.29xl09) of normallevel in the fourteenth day after irradiation. 3. The CD4+ T cells in group A (49.81 + 5.37%) was significantly higher than group B (30.47+4.62%) and group C (31.33 + 5.29%) on dO (PO.05),there was no evident difference between group B and group C(P>0.05);the CDg+ T cells in group A (27.80 + 2.45%) was significantly lower than group B (60.40 + 0.73%) and group C (53.98 + 8.98%)(PO.05),there was no evident difference between group B and group C(P>0.05). 4. The results of MLR showed that the stimulative effect in group A (2264.1 + 118.8) was more stronger than that in group 6(1667.8 + 224.3) and group C( 123 7.0 + 198.5) (P<0.01),but that in group B was more stronger than that in group C(1237.0 + 198.5) ( PO.05 ). 5.1n group C,the expression of the MHC-II antigen of guinea-pig on rat's thymus cells was 17.02 + 5.13% after rejection,but this expression on the same rat's peripheral blood lymphocytes s li...
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