Effects of zinc on cell-mediated immunity in chronic hemodialysis patients

Thirteen healthy subjects and 20 hemodialysis patients were studied to observe the delayed hypersensitivity skin tests (DHSTs) and phytohemagglutinin (PHA)-stimulating lymphocyte blastogenesis. Significant differences were observed between the groups. Controls had a higher proportion of positive skin reaction than hemodialysis patients in relation to Escherichia coli (p<0.01) and tuberculin (PPD) (p<0.05). Regarding lymphocyte blastogenesis stimulated by phytohemagglutinin (PHA), cell proliferation was more accentuated in controls than hemodialysis patients (p<0.05). On the other hand, serum zinc was elevated in controls (78 +/- 8 microg/dL) in comparison to hemodialysis patients (71 +/- 33 microg/dL) (p<0.05). Of the 20 hemodialysis patients, 8 patients were maintained on long-term hemodialysis before and after zinc therapy, with the aim of studying DHST and PHA-stimulating lymphocyte blastogenesis. There was a significant improvement of DHST response to E. coli antigen after 100 d of zinc treatment (p<0.01), and with the discontinuation of therapy, the DHST responses decreased back to the initial values (p<0.05). Zinc administration also increased the lymphocyte proliferation induced by PHA from 31386 +/- 3974 to 42480 +/- 5242 cpm (mean +/- SD) (p<0.05). These results indicated that zinc therapy improved in vivo and in vitro DHST and lymphocyte function of hemodialysis patients and that its discontinuation suppressed all of the benefits observed.