Figure 4.

Glycolipid antigen-processing reactions in cells. Treatment of activated macrophages with trehalose monomycolate, or trehalose dimycolate (TDM, cord factor) does not lead to the activation of glucose monomycolate (GMM) -specific T cells, even though these larger glycolipids contain antigenic GMM as a substructure.¹⁷,⁶⁶ In addition, activated macrophages cannot efficiently glucosylate free mycolic acid (MA) to yield GMM in the absence of mycobacteria. However, mycobacteria growing within cells or tissues can capture glucose from host cells to generate antigenic GMM using a mycolyltransferase that remains to be identified.³² Dendritic cells can use α-galactosidase A to cleave the terminal galactosyl residue of synthetic galactosyl (α1 → α2) α-galactosyl ceramide to generate antigenic α-galacosyl ceramide within the late endosomes or lysosomes of antigen-presenting cells.¹⁹,⁶⁴