Fig. 2

Nutrient uptake and usage by pathways of intermediary metabolism linked to downstream processes. Simplified schema of items discussed in more detail in the body of the text. The extracellular milieux in which B lineage cells reside and through which they pass, in the upper portion of the diagram, may differ in concentrations of key constituents that include glucose, glutamine, essential amino acids (EAAs, i.e., those that cannot be synthesized in the B cells), and fatty acids (both short- and long-chain, i.e., SCFAs and LCFAs). The multiplicity of different transporters used for import (and in some cases export) of these nutrients is omitted from the picture, but as noted in the text, glucose may pass through at least three different molecules whose ratios may be different depending on the B lineage cell type, while glutamine has over four different routes. Several amino acids in addition to glutamine can be fed into mitochondria and the Krebs (TCA) cycle. The branch-point between glycolysis and the pentose phosphate shunt pathway at glucose-6-phosphate (G-6-P) is shown along with the mitochondrial pyruvate channel (MPC) as one route for pyruvate entry and conversion to acetyl-coenzyme A (Ac-CoA), but additional diversions of metabolites prior to ending glycolysis as pyruvate may be possible and are not shown. A suitably balanced combination of protein, nucleotide, and (phospho)lipid synthesis is required for clonal expansion, effector differentiation, and the execution of functions such as secretion of glycosylated antibody molecules, all of which also require energy (ATP)