Lectin that binds beta-galactoside and a wide array of complex carbohydrates (PubMed:1900835, PubMed:8108426, PubMed:7773775). Plays a role in regulating apoptosis, cell proliferation and cell differentiation. Inhibits CD45 protein phosphatase activity and therefore the dephosphorylation of Lyn kinase. Strong inducer of T-cell apoptosis. Homodimer. Binds LGALS3BP. Interacts with CD2, CD3, CD4, CD6, CD7, CD43, ALCAM and CD45. Interacts with laminin (via poly-N-acetyllactosamine). Interacts with SUSD2. Interacts with cargo receptor TMED10; the interaction mediates the translocation from the cytoplasm into the ERGIC (endoplasmic reticulum-Golgi intermediate compartment) and thereby secretion. Can be secreted; the secretion is dependent on protein unfolding and facilitated by the cargo receptor TMED10; it results in protein translocation from the cytoplasm into the ERGIC (endoplasmic reticulum-Golgi intermediate compartment) followed by vesicle entry and secretion.