Common variable immunodeficiency associated with myelocathexis and altered membrane sodium-proton antiport.

Alterations in protein kinase C (PKC) activity have been implied in the pathogenesis of common variable immunodeficiency (CVID). We analyzed amiloride-sensitive red blood cell Na+/H+ exchange (sodium-proton antiport, SPA) and its response to protein kinase stimulation in a patient with CVID. Compared with healthy subjects or patients with sepsis, a unique pattern of SPA activation has been shown. The patient's SPA was decreased and unresponsive to PKC stimulation, whereas stimulation by insulin, a tyrosine kinase activator, restored SPA activity. An alteration of serine-threonine phosphorylation is suggested as a possible mechanism for the immune failure.