Influences of Polyactin A on activities of human immune function in vitro

The newly found immunopotentiator Polyactin A (PAA) developed in China, is a heteropolysaccharide isolated from fermentation both of alpha-hemolytic streptococci strain No 33. In order to understand more deeply the mechanisms of PAA, the effect of PAA on lymphocytes proliferation (LP) and the natural killer (NK) cell activity have been investigated and the results are showed as follows: 1. PAA was shown to stimulate the transformation of lymphocytes from normal subjects and patients with esophageal carcinoma (EC) at 1000 μg.ml ^-1 in vitro. Furthermore, influence of PAA on the blastogenic response of lymphocytes to PHA was found to be effective in promoting proliferation at 100~1000 μg·ml ^-1 in normal subjects and 10~100 μg.ml ^-1 in patients with EC respectively. 2. The NK cell activity and influence of PAA on 30 normal subjects and 16 patients with EC were examined in vitro by ( ³ H)-TdR incorporation assay. Our results demonstrated that pretreatment of peripheral blood lymphocytes (PBL) of normal subjects and particularly the patients with 100 μg.ml ^-1 PAA for 4 hours significantly enhance NK activity up to 12.39 ± 4.5% and 19.66 ± 5.4% respectively (P < 0.001). This enhancement was depended on the concentration of PAA used and time of incubation. In conclusion, PAA may be a potential agent used as a biological response modifier in human.