C-type lectin domain family 5 member A (CLEC5A), also known as C-type lectin superfamily member 5 (CLECSF5) and myeloid DAP12-associating lectin 1 (MDL-1) is a C-type lectin that in humans is encoded by the CLEC5A gene.
 
Structurally MDL-1 is a type II transmembrane protein with a short cytoplasmic tail and without signaling motifs, therefore it requires association with the adaptor protein DAP12 to generate signals via Syk pathway.
MDL-1 is highly expressed on myeloid lineages like neutrophil, monocyte, macrophage and also osteoclast, microglia and dendritic cells.
Activation of MDL-1 induces production of many cytokines (TNF-α, IL-1, IL-6, IL-8 and IL-17A) and chemokines (MIP-1α, RANTES, IP-10, MDC). MDL-1 also amplifies innate immune response.