deficiency = insufficient number ? Or = defectiveness?

Context:

6.4. B-cell deficiencies with identified associations with autoimmunity


Diseases due primarily to a deficiency of B cells and impaired antibody production, with autoimmune expressions, include common variable immunodeficiency disease (CVID, likely comprising a diverse group of disease entities, which is the most frequent symptomatic primary immunodeficiency disease in adults, the hyper-IgM (HIGM) syndrome, thymoma with B-cell deficiency and hypogammoglobulinemia (Good syndrome) and IgA deficiency [28]. The genetically well-characterized X-linked agammaglobulinemia (XLA, Bruton’s disease), resulting from a maturation failure exclusively of B cells, lacks autoimmune associations (a point of interest in itself) and so was not considered at the Colloquium.