Comparative study on antitumor effect of cell-wall skeleton of Mycobacterium bovis BCG and Nocardia rubra, with reference to T-cell dependency and independency.

Antitumor activity induced by the oil-attached cell-wall skeleton of Nocardia rubra (N-CWS) was compared with that of the oil-attached cell-wall skeleton of Mycobacterium bovis BCG (BCG-CWS) in syngeneic BALB/c tumor-host systems. In normal BALB/c mice (+/+), N-CWS exhibited stronger suppressive effect on syngeneic Br-1 and MCA tumors than did BCG-CWS. In athymic nude mice (nu/nu), BCG-CWS was as effective as N-CWS for the suppression of growth of such tumors. Suppressive effect of N-CWS treatment appears to be stronger to some extent in +/+ mice than in nu/nu mice. Immune spleen cells obtained from +/+ mice after footpad inoculation of MCA tumor cells mixed with N-CWS were effective in suppressing the MCA tumor growth, although those obtained from mice after inoculation of MCA tumor cells mixed with BCG-CWS did not exhibit a suppressive effect. This antitumor activity of immune spleen cells may be attributed to tumor-specific killer T cells. The differences of antitumor activities induced by these agents were discussed with reference to T-cell dependency and independency.