Dendritic cell inhibitory and activating immunoreceptors (DCIR and DCAR) in duck: Genomic organization and expression

C-type lectin immunoreceptor genes encoding DC inhibitory and activating receptors (DCIR and DCAR) were identified in a spleen EST library of duck (Anas platyrhynchos). These receptors are of interest for their potential as regulators of antigen presenting cells. A genomic clone was isolated and fully sequenced, containing one DCIR gene and two DCAR genes arranged in tandem order. Duck DCIR encodes an inhibitory receptor that features an immunoreceptor tyrosine-based inhibitory motif (ITIM) in the cytoplasmic domain. DCAR1 is a pseudogene. DCAR2 encodes an activating receptor with a positively charged residue in the transmembrane region. Full-length and alternatively spliced forms of both DCIR and DCAR2 are apparent. Duck DCIR and DCAR transcripts are preferentially expressed in immune and mucosal tissues including spleen, bursa of Fabricius, intestine and lung. Targeting these receptors on dendritic cells holds potential for breaking tolerance or for enhancing immune responses, relevant to the duck model for hepatitis B and vaccination against avian influenza.