Deviant immune responses to allogeneic tumor cells placed into the anterior chamber protect the intraocular neoplasm, but prevent metastases

Intracameral presentation of P815 mastocytoma cells into allogeneic BALB/c mice resulted in a constellation of findings that were seemingly paradoxical. Intracameral inoculated tumors grew progressively, yet the same number of cells injected s.c. failed to grow in normal BALB/c mice. The uncontrolled growth of i.c. allogeneic tumors was accompanied by a profound specific suppression of CMI. In spite of the progressive i.c. tumor growth and the suppressed CMI, extraocular metastases did not develop into fulminant tumors as might be expected. Tumor metastases readily escaped from the anterior chamber but were rejected by T-cell-dependent mechanisms. Moreover, these T-cell-dependent processes also proved to be effective in preventing the growth of secondary tumor challenge inocula of monodisperse P815 cells administered s.c. To account for the fact that i.c. tumors grow progressively, while extraocular tumors fail to develop in the same mice, we suggest that humoral antibodies effectively lyse tumor cells as single-cell suspensions and can prevent metastatic foci from developing. This conclusion is supported by the observation that i.c. injected mice produced high titers of lytic antibodies only after the i.c. tumor had attained a large mass. We assume that the expanding, solid i.c. tumor is impervious to the action of the same antibodies and in the absence of specific CMI, the local tumor grows unimpeded.