Suppression of B16 Melanoma Lung Colonization by Syngeneic Monoclonal Antibodies

Abstract

Syngeneic monoclonal antibodies (MAbs) were produced to B16 melanoma by hybridization of spleen cells from B16-F1 or B16-F10 tumor-bearing C57BL/6J mice. Two antigens were identified by the immunofluorescence reactions of anti-F1 MAbs, 2G10 (IgG₁) and 3C10 (IgM). Both antigens are membrane associated in 97–99% of fixed F1 and F10 cells and are cross-reactive with normal syngeneic thymocytes, and other normal and transformed cultured mouse cells. An anti-F10 Mab, 3E9 (IgG₃), reacts with a membrane antigen found in about 40% of F1 and F10 cells and in all transformed mouse cells tested, but was not found in normal cells. The 3C10 and 3E9 antigens are shed into the medium of cultured cells. ¹²⁵I-Labeled membrane components of M_r 48,000 and 40,000 (3C10) and 25,000 (3E9) were immunoprecipitated. Some 3C10 immunoprecipitates also contained components of M_r 25,000 and 15,000.

The three MAbs were tested for suppression of lung colonization by B16-F1 and B16-F10 metastatic variants in C57BL/6J mice. MAbs were injected 1 day prior to and 1 week after injection of tumor cells. 2G10 was highly suppressive for both B16-F1 and B16-F10 cells. 3C10 and 3E9 were suppressive for B16-F10 cells but were nonsuppressive and enhancing for B16-F1 cells (P ≤ 0.05). A novel immunotherapy model was tested. Delayed hypersensitivity was selectively induced to the 3C10 MAb in C57BL/6J mice by sensitization with lipid-conjugated purified MAb. Sensitized mice were injected with B16 cells and MAb to determine whether a cellular reaction with cell bound MAb in vivo could be suppressive for tumor cells. The treatment was suppressive for B16-F1 lung colonies, but caused augmentation of lung colonies from B16-F10 cells (P ≤ 0.05).