Lymphocyte dysmetabolism: an immunocytochemical comparative approach in IDDM and control subjects

We have investigated by immune-electron microscopy the presence of phosphot yrosine in cells as a whole and in different cell districts (nucleus, cytop lasm, plasma membrane, and mitochondria) in peripheral blood lymphocytes of IDDM (insulin-dependent diabetes mellitus) patients and age-matched contro ls. Immuno-gold particle density was highest in mitochondria and decreased in c ytoplasm, nucleus and plasma membrane. The time dependence of phosphotyrosi ne labelling after cell isolation was very strong in all subcellular popula tions, with a fall in immunogold staining after 30 min. Staining levels at zero time were similar in controls and IDDM patients; th e loss of phosphotyrosine labelling was much stronger in controls, except i n the plasma membrane. Plasma membrane NADH oxidoreductase activity, studied using cytosolic NADH as substrate and assayed with DCIP as acceptor, was significantly increased in IDDM patients, suggesting a response to a deficient mitochondrial energ etic activity. The fact that NADH oxidoreductase is a growth factor related to tyrosine ph osphorylation pathways raises intriguing questions on the cellular derangem ent occurring in peripheral lymphocytes in IDDM, although the relationships among the immunocytochemical and biochemical changes is still obscure.