Pilot study of low-dose azathioprine in presensitized patients awaiting heart or lung transplantation

In an effort to reduce the level of presensitization in patients on our heart and lung transplant waiting list, ten patients with random panel reactivity above 10% on monthly screening for durations of 2 to 59 months were given low-dose azathioprine (25 to 75 mg/day) for 1 to 22 months. All patients had positive T-cell panel reactivity (10% to 70%) against specific (n = 6), multi-specific (n = 1), or undefined (n = 3) HLA loci, and four additional patients had positive B-cell panel reactivity (5% to 40%). No effect of azathioprine on panel reactivity was seen in four of ten patients (40%), whereas a significant and sustained reduction in panel reactivity occurred in six patients (60%), all within 2 months of commencing azathioprine. All nonresponders had antibodies with class I (A locus) specificity, whereas all six responders had multi-specific or undefined antibody specificities. A formal trial of low-dose azathioprine in presensitized recipients is warranted.