Immunisation with citrullinated rat serum albumin (Cit-RSA) breaks immunological tolerance on the B cell side. Immunisation with Cit-RSA (white bars) induced an antibody response against Cit-RSA (a), cross-reacting with unmodified rat serum albumin (RSA) (b) at all time points investigated, whereas immunisation with RSA (black bars) did not. Sera were collected 12, 24, 35 and 61 days after immunisation, and total IgG was measured by ELISA as OD at 405 nm. Results are means ± SD (n = 7 animals per group), representative of two replicate experiments. **P < 0.01 at all time points.