Mitochondrial respiration in B lymphocytes is essential for humoral immunity by controlling the flux of the TCA cycle

To elucidate the function of oxidative phosphorylation (OxPhos) during B cell differentiation, we employ CD23Cre-driven expression of the dominant-negative K320E mutant of the mitochondrial helicase Twinkle (DNT). DNT-expression depletes mitochondrial DNA during B cell maturation, reduces the abundance of respiratory chain protein subunits encoded by mitochondrial DNA, and, consequently, respiratory chain super-complexes in activated B cells. Whereas B cell development in DNT mice is normal, B cell proliferation, germinal centers, class switch to IgG, plasma cell maturation, and T cell-dependent as well as T cell-independent humoral immunity are diminished. DNT expression dampens OxPhos but increases glycolysis in lipopolysaccharide and B cell receptor-activated cells. Lipopolysaccharide-activated DNT-B cells exhibit altered metabolites of glycolysis, the pentose phosphate pathway, and the tricarboxylic acid cycle and a lower amount of phosphatidic acid. Consequently, mTORC1 activity and BLIMP1 induction are curtailed, whereas HIF1α is stabilized. Hence, mitochondrial DNA controls the metabolism of activated B cells via OxPhos to foster humoral immunity.

[Biomechanical consequences of a knee osteoarthritis on the opposite lower limb]

The aim of this work was to study the compensatory strategies built up by patients with unilateral knee arthritis during stair descent. These compensatory strategies might induce increased biomechanical constraints on the unaffected knee.

METHOD

A kinetic and kinematic analysis was performed in 11 patients with unilateral knee arthritis and in 14 control subjects using an ELITE system and two force-plates. The peak of vertical ground reaction forces when landing on the reception force-plate, the time to reach the peak and the duration of the different phases of the movement were studied during stair descent.

RESULTS

The peak of vertical ground reaction forces was more important when landing on the unaffected limb than when landing on the affected limb. The time to reach this peak was longer in patients than in controls no matter which side was supporting. The duration of the single support phase was longer on the unaffected limb than on the affected limb.

DISCUSSION AND CONCLUSION

This work has shown that patients with unilateral knee arthritis develop new strategies during stair descent. These new strategies imply increased biomechanical constraints on the unaffected limb and might favor arthritis on the sound side. These results support the idea that rehabilitation protocols of patients with unilateral knee arthritis should also involve the unaffected limb.