Biological activity of anti-CEA Fab-H-2K^b/ova conjugate. (A) Demonstration by cytofluorometry of the specific coating of CEA+ human LoVo colon carcinoma cells by anti-CEA Fab-H-2K^b/ova conjugate. The conjugate was revealed by a FITC-labeled anti-H-2K^b mAb (solid line). The negative control consisted of LoVo cells treated with the anti-H-2K^b and the FITC-labeled anti-murine IgG (black area), while the positive control consisted of LoVo cells coated with the anti-CEA mAb 35, followed by FITC-labeled anti-murine Ig antibody. (B) Specific lysis of ⁵¹Cr-labeled CEA-expressing human LoVo colon carcinoma cells (black squares) or MC38-CEA+ colon carcinoma cells (black circles) precoated with the anti-CEA Fab-H-2K^b/ova conjugate and incubated with ova specific H-2K^b T cells at the indicated T cell/target cell ratio. Negative controls were uncoated LoVo (open squares) and murine MC38-CEA+ (open circles) cells.