CD1b: ProductsCD1b is an approximately 40-50 kDa transmembrane glycoprotein in the CD1 family of glycolipid antigen-presenting MHC-like molecules. CD1b associates with beta2-microglobulin in endosomes and the Golgi where it facilitates the processing of glycolipids for their presentation by other CD1 family proteins. CD1b is expressed by most nonhuman mammals but not by mice or rats. It contains one Ig-like domain in its extracellular region. Alternate splicing of human CD1b generates an additional isoform that lacks 55 amino acids of the Ig-like domain.