LIR9 amino acid sequences and LIR9 expression in leukocytes and transfected cells.

(A) Alignment of the amino acid sequences of the 4 forms of LIR9 and LIR6b, another activating LIR with 2 immunoglobulinlike domains. Two arrows indicate the predicted cleavage sites for the signal peptides; the first arrow indicates the cleavage site for LIR9m1 and LIR9s1, and the second arrow indicates the cleavage site for LIR9m2 and LIR9s2. The box highlights the 12 amino acid exon that is present in LIR9m1 and LIR9s1. Underlined amino acids are N-linked glycosylation sites. The arginine residue within the transmembrane domain is shown in boldface. (B) Expression of LIR9m (1 and 2) and LIR9s (1 and 2) transcripts in peripheral blood leukocytes and in monocyte-derived dendritic cells as determined by TaqMan quantitative reverse transcription–polymerase chain reaction (RT-PCR). Data are expressed on a relative scale using the LIR9s expression in monocytes as the reference value. (C) LIR9m expression in CD14⁺ monocytes as determined by 2-color fluorescence-activated cell sorter (FACS) analysis. (D) LIR9s1 is detected in the conditioned media of COS cells transfected with the LIR9s1 cDNA, but not with the LIR9m1 cDNA or with empty vector. Cells were transfected with the indicated plasmids and 2 days later were metabolically labeled with³⁵S-(cysteine-methionine) for 5 hours. Ten microliters conditioned media were loaded per lane, and the gel was exposed to film for 49 hours. Arrow indicates the LIR9s1 protein.