Immunogen: Synthesized 23-amino acid peptide, SLLTEVETPIRNEWGCRCNDSSD, the ectodomain of matrix protein 2 (M2e) of the influenza A virus (A/Brisbane/10/2007/H3N2) (GenBank accession# ACO95272). Specificity: Reacts with the matrix protein 2 of influenza A that contains the same ectodomain sequence, such as A/Hong Kong/4801/2014 (H3N2).