The effects of LaCl_3 and GdCl_3 on primary mouse immune cells in vitro were studied. The results indicated that GdCl_3(0.001-10 μmol/L) promoted the proliferation of the spleen cells. LaCl_3 had no effect on proliferation of the spleen cells at the concentrations of 1 and 10 μmol/L, but promoted the proliferation of the spleen cells at other concentrations. LaCl_3(0.001, 0.01, 1, and 10 μmol/L) promoted the proliferation of T lymphoid cells stimulated by concanavalin A (ConA). GdCl_3 inhibited the proliferation of T lymphoid cells stimulated by ConA at concentration of 0.001 μmol/L, had no effect on the proliferation of T lymphoid cells at the concentrations of 0.01, 0.1 and 1 μmol/L, but turned to promote the proliferation of T lymphoid cells at the concentration of 10 μmol/L. LaCl_3 and GdCl_3 inhibited the proliferation of B lymphoid cells stimulated by lipopolysaccharides (LPS) at the concentration of 0.1 μmol/L, but they promoted the proliferation of B lymphoid cells at other concentrations. For 4 h, LaCl_3 had no effect on NK cell activity at the concentration of 0.001 μmol/L, but promoted NK cell activity at other concentrations. GdCl_3(0.001, 0.01, 0.1,1, and 10 μmol/L) promoted NK cell activity. For 8 h, LaCl_3 inhibited NK cell activity at the concentrations of 0.001 and 0.01 μmol/L, promoted NK cell activity at the concentrations of 0.1 and 1 μmol/L, but had no effects on NK cell activity at the concentrations of 10 μmol/L. GdCl_3 inhibited NK cell activity at the concentration of 1 μmol/L, but it promoted NK cell activity at other concentrations. The results suggest that the effects of LaCl_3 and GdCl_3 on primary immune cells in vitro depend on time, concentration and their species.