Effect of haptoglobin (Hp) on cell migration and calcium release in pre-B lymphocytes 300.19 stably expressing chemokine (C-C motif) receptor 2 (CCR2) (300.19-CCR2). (a) Chemotaxis was performed on 300.19 and 300.19-CCR2 cells for 3 h at the indicated doses of Hp and monocyte chemoattractant protein 1 (MCP1). Bovine serum albumin (BSA) (1 mg/ml) was used as negative control. Two-way analysis of variance (ANOVA), P < 0.0001. Bonferroni post-test versus BSA ***P < 0.001, versus 300.19 parental cells §§§P < 0.001. (b) Left panel, fura-2 acetoxymethyl ester (fura-2 AM) preloaded 300.12-CCR2 cells untreated or pretreated with 5 μM RS102895 were stimulated with 250 ng/ml MCP1 or 0.5 mg/ml Hp, right panel quantification of [Ca2+]i rise in 300.19-CCR2 cells. The rate of [Ca2+]i rise (percentage fura-2 saturation/s) induced by MCP1 was set to 100% and the rate after pretreatment was calculated. At the bottom on the left, stimulation of 300.19 parental cells did not result in any appreciable calcium flux. The results are representative of three independent experiments.