Nature Reviews Immunology 3, 621–629 (2003)

In the legend to Figure 5 on page 627, the incorrect references are cited. The legend should state that the second pathway includes ideas from Refs 56 and 59. These references are as follows:

56. Lindner, R. & Unanue, E. R. Distinct antigen MHC class II complexes generated by separate processing pathways. EMBO J. 15, 6910–6920 (1996).

59. Villadangos, J. A., Driessen, C., Shi, G. P., Chapman, H. A. & Ploegh, H. L. Early endosomal maturation of MHC class II molecules independently of cysteine proteases and H–2DM. EMBO J. 19, 882–891 (2000).

Also, on page 627 (right-hand column, second paragraph, line 10), the text should read '(TCR)-interaction positions −1 and 11' not '(TCR)-interaction positions −1 and −11'.

The online version of this article has been corrected.