Frequency of Murine Cytotoxic T Cell Precursors Reactive to Plasma Cell Tumour‐associated Antigens as Compared to Major Histocompatibility Antigens

Abstract

Summary The frequency of cytotoxic T lymphocyte precursors (CTL‐P) reactive to plasmacytoma (PCT) tumour‐associated antigens (TAA) was studied in BALB/c mouse spleen. Progressively decreasing numbers of responder BALB/c spleen cells were cultured with mitomycin C‐treated stimulator MPC‐11 BALB/c PCT cells, and a Poisson analysis was performed of the wells scored positive in a 51Cr release assay with PCT target cells. It was found that approximately 2 per million BALB/c spleen cells were CTL‐P reactive to TAA of MPC‐11, and about one in three of these precursors responded to a TAA expressed by MPC‐11 which was shared with the C3H PCT C1.18. The frequency of CTL‐P reactive to TAA was shown to be 30 to 500 fold lower than that for CTL reactive to various major histocompatibility complex alloantigens, and the addition of exogenous Interleukin‐2 only resulted in a 2‐3 fold increase in this CTL‐P frequency. These results suggest that the weak levels of tumour immunity induced in vivo by immunisation of BALB/c mice with MPC‐11 are, at least in part, due to a very low frequency of CTL‐P reactive to TAA of that PCT.