Promotion of incidence of adenovirus type 12 transplantable tumors by carrageenan, a specific antimacrophage agent.

Carrageenan, a sulfated polygalactose with known macrophage-toxic properties, was used to ascertain the role of macrophages in resistance to adenovirus type 12 transplantable tumors. A single ip injection of 5 or 10 mg carrageenan led to increased incidence and more rapid growth of tumors in C3H mice. Carrageenan was most effective if given 1 day before tumor inoculation; the effectiveness decreased with increasing intervals before or after tumor cell injection. The macrophage stabilizer poly-2-vinylpyridine N-oxide injected sc (150 mg/kg) 1 day before carrageenan was given reduced the incidence of tumors. These data lend further support to the importance of macrophages in tumor immunity.