Infiltration and accumulation of precursor cytotoxic T-cells increase with time in progressively growing ocular tumors.

ABSTRACT

Precursors of cytotoxic T-cells (pTc) infiltrate P815 tumors growing progressively within the immunologically privileged anterior chamber (AC) of BALB/c mouse eyes, but directly cytotoxic T-cells cannot be detected in these eyes. To determine if the failure to reject these tumors is due to a relative inability of tumor-specific pTc to gain access to, or be retained by, the tumor-containing eye, we have assayed through time the frequency of pTc in eyes that received P511 tumor cells in the AC or subconjunctival space (SC; a site where the tumors are rejected). P511 tumor cells, a hypoxanthine-amethopterin-thymine medium-sensitive derivative of P815 cells, were selected for these studies because P511 tumor cells can be eliminated from in vitro lymphocyte cultures containing hypoxanthine-amethopterin-thymine medium, permitting us to make accurate estimates of pTc frequencies. To ensure that P511 cells are similar biologically and immunologically to P815 tumor cells, we demonstrated that both P511 and P815 cells form progressively growing tumors when injected into the AC of BALB/c eyes and that recipients of both tumor cell lines develop DBA/2-specific anterior chamber-associated immune deviation. Using cell suspensions harvested from eyes of mice bearing AC or SC P511 tumors, we found that tumor-specific pTc appeared first (day 8) in SC tumor-bearing eyes, compared to their appearance in AC tumor-bearing eyes (day 11). Thereafter, however, the number of pTc detected was significantly greater in eyes bearing progressively growing AC tumors than in SC tumor-injected eyes. The number and frequency of pTc we found in these eyes appeared to correlate directly with the size of the ocular tumor burden. We conclude that failure to reject P511 tumor from the AC can be ascribed neither to a quantitative deficiency in infiltrating tumor-specific pTc nor to an inability to retain pTc at the site. Our findings suggest that immune acceptance of allogeneic ocular tumor grafts may result from failure of infiltrating pTc to differentiate terminally in situ into cytotoxic effector cells.