LLT1 was also found to be expressed by cells of the monocyte/macrophage lineage rheumatoid arthritis (RA) patients and serum levels of soluble LLT1 were increased in all patient groups (patients with early- and late-stage RA, seropositive arthralgia and spondyloarthropathy) when compared to healthy subjects [33]. Here, CLEC2D is linked to rheumatoid arthritis.