Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

The streptcoccal agent OK-432, an inactivated and lyophilized preparation of a low-virulence strain (Su) of Streptococcus pyogenes (group A) that was developed by Okamoto et al. (1), is commonly used as an immunopotentiator for immunotherapy in malignant diseases. Accumulated evidence suggests that OK-432 exerts antineoplastic effects by a direct cytotoxic or inhibitory effect on tumor cells (2-4), as well as by a stimulatory effect on immunocompetent cells such as macrophages and natural killer (NK) cells in experimental studies including human (5-8). In addition, it has been reported that OK-432 induces various cytokines such as interferon (IFN), interleukin (IL)-2, as well as tumor necrosis factor (TNF) in mice and humans (9-13). It is well known that IFN functions as an important regulator of NK cells and macrophages (14-19).

However, it is still unknown what component(s) in OK-432, a whole bacterial preparation, plays an important role for cytokine induction as well as antitumor effect. To isolate the major compornent for the immunomodulatory effect of OK-432, we have generated TS-2 monoclonal antibody which neutralizes IFN-g-inducing activity of OK-432. TS-2 also recognized lipoteichoic acid (LTA) derived from Streptococcus pyogenes. Then, we isolated the LTA-related molecule (OK-PSA) from the butanol extract of OK-432 by an affinity chromatography on CNBr-activated Sepharose 4B-bound TS-2 (20). In the present study, cytokine-inducing activity of OK-PSA was examined by the in vitro system using human peripheral blood mononuclear cells (PBMC).

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