PROLONGATION OF CONCOMITANT ANTITUMOR IMMUNITY IN MICE TREATED WITH Z-100, AN ARABINOMANNAN EXTRACTED FROM MYCOBACTERIUM-TUBERCULOSIS

The effect of Z-100, a natural immunomodulator extracted from Mycobact erium tuberculosis strain Aoyama B, on concomitant antitumor immunity (CAI) was investigated in mice immunized with Meth-A tumor cells (prim ary inoculation) in combination with Corynebacterium parvum. CAI, whic h was observed in mice 10 days after immunization (I10 mice), disappea red in mice 20 days after immunization (120 mice). However, no growth of secondarily inoculated Meth-A tumors was demonstrated in I20 mice t reated with Z-1 00 (IZ20 mice). CAI was demonstrated in tumor-bearing recipients when splenic mononuclear cells (SMNC) from 110 mice or IZ20 mice were transferred to recipients intralesionally. However, CAI was not detected when recipients received SMNC from 120 mice or a SMNC mi xture from 110 and 120 mice. The SMNC mixture from I10 and IZ20 mice i nhibited the growth of Meth-A solid tumors in the recipients. The acti vity of nonspecific suppressor cells, which were characterized as CD8 T cells, was demonstrated in SMNC from 120 mice, while SMNC from I10 and IZ20 mice did not show any suppressor cell activities. In addition , clear inhibition of tumor growth was demonstrated in recipient mice which received a SMNC mixture from 120 mice, previously treated with a nti-Lyt-2+ MAb plus complement, and I10 mice. These results suggest th at Z-100 might be able to prolong CAI observed in I10 mice through the inhibition of Lyt-2+ T suppressor cells detected in SMNC from 120 mic e.