Changes in serum and urine lysozyme activity after kidney transplantation: influence of graft function and therapy with azathioprine.

We investigated changes in lysozyme activity in serum and urine of kidney-transplant patients, and found that the production and catabolism of lysozyme in such patients differs markedly from that in normal subjects. Resumption of graft function decreases the high serum lysozyme activity by increasing the rate of catabolism in the transplant; at the same time, however, the production is inhibited by therapy with azathioprine. Changes in serum lysozyme activity correlate well with leukocyte count; thus its determination might be useful in monitoring immunosuppression. The urinary excretion of the enzyme, although not specific to rejection, is a good index of the degree of tubular damage.