New Resarch Regarding Development of Autoimmunity in Patients with CVID

The results of a CVID study were recently published in the Journal of Clinical Investigation. In this study, Yale researchers Eric Meffre and his colleagues found that CVID patients with a single mutation in the tumor necrosis factor receptor superfamily (TACI) led to development of autoimmune diseases; whereas those with two mutations of TACI did not develop autoimmune diseases.

"When associated with CVID, a single TACI mutation predicts the development of autoantibody-mediated autoimmune disease, whereas patients with two mutated alleles are mostly spared clinical autoimmune conditions, suggesting a complex role for TACI in maintaining B cell tolerance" (From article: CVID-associated TACI mutations affect autoreactive B cell selection and activation, Published September 24, 2013)

A recent article published by Science Codex (Development of Autoimmunity in Patients with Common Variable Immune Deficiency) explained the findings more clearly for those of us without advanced biology degrees: 

"The (research study) authors found that CVID patients with a single altered TACI allele maintained some residual B cell responsiveness that promoted development of autoantibodies, whereas individuals with 2 mutated copies of TACI have complete impairment of B cell responses, which likely prevents autoimmunity."

My question, is it truly better to have total impairment of B cell responses? I grant that being free of autoimmune diseases is a blessing, but what about the little infection-fighting that we have with some B cell responsiveness? I don't understand the biological terminology in the Journal of Clinical Investigation article enough to tell whether there is enough B cell responsiveness left in people with only one TACI mutation to fight infections. If so, which is more beneficial? At the very least this research answers some of our questions about why we can develop autoimmune diseases with broken immune systems. For those of us with CVID, answers are truly a gift. Thank you, Eric Meffre and colleagues for your efforts.