Suppression of mixed leukocyte culture using leukocytes from normal individuals, uremic patients, and allograft recipients

The suppressor cell function of peripheral blood mononuclear leukocytes (MNLs) from normal individuals, renal failure patients, and allograft recipients was evaluated using a suppressor cell assay wherein putative suppressors were added at the initiation of a third-party, one-way mixed leukocyte culture (MLC). MNLs from renal allograft recipients displayed the greatest suppressive activity (P less than 0.05): 50% suppression was achieved with 0.5 x 10(5) MNLs from allograft recipients, 2 x 10(5) MNLs from end stage renal disease patients, or 4 x 10(5) MNLs from normal individuals. The frequency of tests displaying positive MLC suppression using 1 x 10(5) MNLs was 90% (383 of 426) for allograft recipients compared with 60% (83 of 138) for renal failure patients and 28.2% (29 of 103) for normal individuals (P less than 0.01). The suppression displayed by 1 x 10(5) MNLs from potential allograft recipients receiving more than five pretransplant blood transfusions (BTs) was equal to that of 4 x 10(5) MNLS from patients receiving less than five BTs (P less than 0.05). Moreover, the frequency of positive MLC suppression from patients treated with more than five versus less than five BTs was 80% versus 40% (P less than 0.001). Although suppression of MLC appeared to be mainly dependent on an esterase (+)-adherent cell, there was no significant difference between the percentage of esterase (+) cells in unfractionated MNLs from the three groups of individuals, suggesting that MLC suppression was attributable to the functional performance rather than the number of suppressor MNLs. Preliminary data suggest a relationship between the level of MLC suppressive activity detected pretransplant and the outcome of the allograft at 6 months.