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                                                                      Exhibit 18

PricewaterhouseCoopers LLP
One Post Office Square
Boston, MA 02109


March 11, 2004


Board of Directors
AVANT Immunotherapeutics, Inc.
119 Fourth Avenue
Needham, MA  02494

Dear Directors:

We are providing this letter to you for inclusion as an exhibit to your Form
10-K filing pursuant to Item 601 of Regulation S-K.

We have audited the consolidated financial statements in the Company's Annual
Report on Form 10-K for the year ended December 31, 2003 and issued our report
thereon dated February 18, 2004. Note 1 to the consolidated financial statements
describes a change in accounting principle from the capitalization of patent
application fees to expensing of patent application fees. It should be
understood that the preferability of one acceptable method of accounting over
another for patent application fees has not been addressed in any authoritative
accounting literature, and in expressing our concurrence below we have relied on
management's determination that this change in accounting principle is
preferable. Based on our reading of management's stated reasons and
justification for this change in accounting principle in the Form 10-K, and our
discussions with management as to their judgment about the relevant business
planning factors relating to the change, we concur with management that such
change represents, in the Company's circumstances, the adoption of a preferable
accounting principle in conformity with Accounting Principles Board Opinion No.
20.

Very truly yours,

/s/ PricewaterhouseCoopers LLP

PricewaterhouseCoopers LLP