Using125I-UDR labelled K562 cells as target cells, we assay the natural killer cell （NK） activity in peripheral blood mononuclear cells （PBMCs） from 36 cases of various types of viral hepatitis B （HB）, together with 33 healthy adults as controls. At same time the NK activity was detected when PBMCs were pretreated with recombinant IL-2 （rIL-2） in 19 patients with various types of HB and 14 normal controls. We also determined the IL-2 activity produced by PBMCs in 26 HB patients and 14 normal controls. The following results were obtained: （1） The NK activity was markedly elevated in early acute hepatitis B （AH） （P0.01）; significantly decreased in chronic active hepatitis （CAH）, chronic persistent hepatitis （CPH） and fulminant hepatitis （FH） （P0.01）, while that of convalescents with AH was within normal range 35.85±12.52%. （2） The early rise of NK activity in acute infection and the decline in convalescence and also the parallel change in SGPT level in 3 AH cases were observed. （3） The amount of IL-2 produced by PBMCs in HB patients was lower than that of normal controls （P0.01 ）. （4）There was no correlation between the change of IL-2 activity and NK activity in HB patients （r=0.15; PO.05）. （5） The NK activity of most normal subjects were enhanced when the PBMCs were pretreated with rIL-2 but the latter was still within the normal ranges. These results suggest that the mechanism of the effect of IL-2 in modulating the NK activity of HB patients is very complicated. IL-2 not only directly enhances the low NK activity of HB patients, but also depresses the high NK activity. This immunomodulating effect may be influenced by serum inhibitory facts as well as the amount and the combining ability of IL-2 receptor or on NK cell surface.
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