Eukaryotic cells express multiple adhesion molecules. In human cells, the major classes are named integrins, members of the Ig superfamily , cadherins, and selectins. Each of these adhesion molecules has a different function and recognizes different ligands. Defects in cell adhesion often result from defects in expression of adhesion molecules, but an unwanted increase in adhesion molecules may impair normal blood flow. The Ig and CAM family includes the calcium independent molecules N-CAM , ICAM, VCAM-1, PE-CAM, L1-CAM, and the integrins LFA-1 (CD11a+CD18), Integrin alphaXbeta2 (CD11c+CD18), Macrophage-1 antigen (CD11b+CD18), VLA-4 (CD49d+CD29), Glycoprotein IIb/IIIa (ITGA2B+ITGB3). The Calcium dependent molecules include the Cadherins and selectins (E-selectin, L-selectin and P-selectin). Changes in the levels of adhesion molecules in plasma are often correlated with pathology.