The grafts from HLA-identical siblings had the highest survival rates (Figure 1). The survival rate of parental-donor grafts with one HLA-haplotype mismatch at three years was 9 percentage points lower than that of grafts from HLA-identical siblings. The survival rates of both spousal grafts and grafts from other living unrelated donors with two HLA-haplotype mismatches were similar to that for parental-donor grafts with one HLA-haplotype mismatch rather than that for cadaveric grafts with two HLA-haplotype mismatches. Despite the fact that the HLA matching was better for the cadaveric grafts (average number of HLA-A, B, and DR mismatches, 3.6) than for spousal grafts and grafts from other living unrelated donors (average number of HLA-A, B, and DR mismatches, 4.1), the survival of the cadaveric grafts was poorer.

The number of HLA mismatches expected on a random basis was computed to be 4.5 on the basis of random pairings of donors and recipients. Thus, there was some small degree of selection against poorly mismatched pairs in the spousal and nonspousal unrelated transplant groups. The level of HLA matching for the cadaveric grafts was higher, as a result of kidney allocation under the UNOS point system, which encourages better-matched transplants. Thus, the higher rate of survival of spousal grafts and grafts from other living unrelated donors as compared with cadaveric grafts cannot be attributed to superior matching.

The survival of grafts from unrelated donors was comparable to that of parental-donor grafts despite the average of 4.1 HLA mismatches in the former group, as compared with 2.3 HLA mismatches in the latter group. Therefore, the high rate of survival of the unrelated-donor grafts was not due to HLA matching that was similar to that of the parental-donor grafts. Nevertheless, there was an effect of HLA matching on the survival of spousal grafts; no rejections occurred before hospital discharge in 93 percent of the recipients of spousal grafts with no HLA-DR mismatches, in 77 percent of the recipients of grafts with one HLA-DR mismatch, and in 70 percent of the recipients of grafts with two HLA-DR mismatches.

The survival rates of cadaveric grafts that functioned from the first day, so that the recipient did not require dialysis, approached those of grafts from living unrelated donors (Figure 1). Cadaveric grafts that failed to function immediately or in which function was delayed, so that the recipient required dialysis in the first week, had a lower survival rate. These results indicate that some of the cadaveric grafts were damaged. When they were removed from the analysis, the survival rate approached that of grafts from living unrelated donors.

Figure 2. Figure 2. Graft Survival among Recipients of Kidneys from Spousal Donors. Husband-to-wife grafts were subgrouped according to whether the wife had previously been pregnant. For eight of the wives, the number of pregnancies was not known.

The three-year survival rate of spousal grafts was 85 percent. Among the spousal donors, 2.6 times as many wives as husbands were donors (Figure 2). The survival rates of wife-to-husband grafts were the same (87 percent) as those of husband-to-wife grafts if the wife had not been pregnant. However, if the wife had been pregnant, graft survival was worse but not significantly so (76 percent, P = 0.40). Among the wives, 21 percent were immunized, as indicated by serum reactivity to lymphocytes of more than 10 percent of randomly chosen persons. This rate of reactivity may be low because wives with reactivity to their husbands' lymphocytes may have been excluded from consideration for transplantation. Reactivity status notwithstanding, the graft outcome was not different between wives who were sensitized and those who were not (P = 0.65).

A comparison of the survival of grafts from unrelated donors with the survival of grafts from recipients' children revealed that the three-year survival of 696 offspring-to-mother grafts was 80 percent, as compared with 82 percent for 99 husband-to-wife transplants. In addition, for 715 offspring-to-father grafts, the three-year graft survival was 84 percent, as compared with 87 percent for 261 wife-to-husband grafts. Thus, the survival rates of spousal grafts from biologically unrelated persons were similar or even slightly higher than those of the offspring-to-parent grafts with one HLA-haplotype mismatch. Among the spousal grafts, the three-year survival rates were 86 percent in the 290 white recipients and 82 percent in the 78 black recipients.

Figure 3. Figure 3. Survival of First Cadaveric Grafts According to Urine Flow on the First Day. The grafts were further grouped on the basis of the number of HLA-A, B, and DR mismatches. The spousal-donor group is included for comparison.

The effect of HLA matching on cadaveric grafts grouped according to whether diuresis occurred on the first day after transplantation is shown in Figure 3. only among the uncompromised cadaveric grafts with 0 HLA-A, B, and DR mismatches were the survival rates similar to those of the spousal grafts. Regardless of the degree of matching, the survival rates of grafts that functioned on the first day were higher than the rates of those that did not. The survival rate of grafts mismatched for all six antigens that functioned on the first day was higher than that of a perfectly matched graft that did not function immediately. Thus, the survival rate of compromised grafts, despite their being HLA-matched, was lower than that of a poorly matched graft that functioned immediately. Nevertheless, there was a stepwise gradation in graft survival according to the degree of mismatching for cadaveric grafts regardless of functional status on the first day, indicating that HLA matching was still valuable for all categories of cadaveric transplants.

Preoperative transfusions increased the three-year rate of survival of spousal grafts: the rate was 81 percent for the 188 recipients who did not undergo transfusion and 90 percent for the 167 who received 1 to 10 transfusions (P = 0.008). In this analysis, 13 recipients who received more than 10 transfusions were excluded since their high transfusion requirement may have reflected the presence of other medical complications.

Figure 4. Figure 4. Survival of Kidney Grafts According to Donor Age. The age distribution of the donors is shown in the inset.

Since the living unrelated donors were younger than the typical cadaveric donors, we compared the rate of graft survival according to donor's age (Figure 4). The survival rates of grafts from living donors were higher than those of cadaveric grafts within each age category.

Short periods of cold ischemia of three to six hours among 1394 cadaveric grafts led to a one-year graft-survival rate of 80 percent, as compared with 91 percent among spousal grafts. Among 5308 cadaveric grafts subjected to 6 to 12 hours of cold ischemia, the one-year graft-survival rate was 84 percent; among 18,383 grafts subjected to 12 to 24 hours of cold ischemia, the rate was 83 percent. Thus, graft survival was not influenced markedly by cold-ischemia times of less than 24 hours.