A human lactoferrin-specific cell line was generated in CBA mice, sensitized with 200 microg HLF in Freund's complete adjuvant. HLFK1 cells derived from the lymph nodes of these mice were maintained using HLF as the antigen. HLF was added at the beginning of each 14-day restimulation cycle, at a concentration of 100 microg/ml. The presentation of the antigen to HLFK1 was demonstrated using glass-adherent lymphocytes from spleens (GAL) as the antigen-presenting cells (APC). The presentation of HLF by GAL was highly efficient; a very low concentration of the antigen (1 microg/ml) was enough to stimulate proliferation of the HLFK1 cell line. HLFK1 did not proliferate in the presence of ovalbumin or bovine lactoferrin (BLF), which is structurally related to HLF. However, we found that BLF caused a reduction in the proliferation of the HLFK1 cell line when BLF was added to the cultures together with the antigen - (HLF). On the other hand, proliferation of the HLFK1 cell line was not inhibited by pretreatment of the antigen-presenting cells or T cells with BLF. Therefore, we suggest that bovine lactoferrin may interfere with the binding or uptake of the antigen (HLF). Alternatively, BLF may nonspecifically inhibit the activation of the HLFK1 cell line.