<p>Animal lectins display a wide variety of architectures.They are classified according to the carbohydrate-recognitiondomain (CRD) of which there are two main types, S-type and C-type.</p><p>C-type lectins <db_xref db="INTERPRO" dbkey="IPR001304"/> display a wide range of specificities.They require Ca<sup>2+</sup> for their activityThey are found predominantly but not exclusively in vertebrates.</p><p>They can be classified into a number of subgroups based on their function and structure:<li> Endocytic lectins - Membrane-bound receptors that mediate endocytosis of glycoproteins</li><li> Collectins - Represented by the soluble mannose-binding proteins of mammalian serum and liver </li> <li>Selectins - Membrane-bound proteins involved in inflammation. There are three main divisions, CD62E, CD62 L and CD62P [<cite idref="PUB00001115"/>].</li></p><p>CD62E (also called E-selectin, ELAM-1 or LECAM-2), CD62L (also called L-selectin, LAM-1, LECAM-1, Leu-8, MEL-14 or TQ-1) and CD62P (also called P-selectin, granule membrane protein-140, GMP-140 or platelet activation dependent granule-external membrane protein, PADGEM) belong to this group.CD62E mediates leukocyte rolling on activated endothelium at inflammatory sites and may also support tumor cell adhesion during hematogenous metastasis, and play a role in angiogenesis. CD62L mediates lymphocyte homing to high endothelial venules of peripheral lymphoid tissue and leukocyte rolling on activated endothelium at inflammatory sites. Interaction of CD62P with PSGL-1 mediates tethering and rolling of leukocytes on the surface of activated endothelial cells, the first step in leukocyte extravasation and migration towards inflammations. CD62P mediates rolling of platelets on endothelial cells and CD62P-mediated interactions are also involved in platelet-mediated delivery of lymphocytes to high endothelial venules.</p><p>Members of the selectin superfamily have the same domain structure: an N-terminal lectin domain followed by an EGF repeat; a variable number (between 2 and 9) of complement regulatory elements; a single trans- membrane region; and a short cytoplasmic anchor. Some studies have found distinct carbohydrate structures on leukocytes that are adhered to by selectins, suggesting that selectins are involved in the selective trafficking of blood-borne components of the immune system.</p><p>CD molecules are leucocyte antigens on cell surfaces. CD antigens nomenclature is updated at Protein Reviews On The Web (http://prow.nci.nih.gov/).</p>