Evaluation of B Lymphocyte Deficiencies

Abstract

The most common of the primary immunodeficiency diseases are those that involve inadequate antibody production. The characteristic presentation of these disorders is recurrent sinopulmonary infections. An arrest in B cell development at the pre-B cell stage leads to agammaglobulinemia and an insignificant number of B cells. X-linked agammaglobulinemia is the most common of these developmental arrests while the autosomal recessive agammaglobulinemias comprise a small minority of the total cases. Likewise, the most common form of the hyper-IgM syndromes (CD40 ligand deficiency) is X-linked. Of the autosomal recessive forms, CD40 deficiency is basically identical to the X-linked form in its clinical phenotype where, in addition to inadequate antibody production, there is defective T cell signaling through the CD40-CD40L interaction. Aside from CD40 deficiency, the other recessive forms of hyper-IgM syndrome have adequate T cell function. IgA deficiency is the most common and the most benign of the B cell disorders. Common variable immunodeficiency is diverse in its presentation and clinical course. The pathophysiology of this disease is multifactorial and frequently ill defined, often making it a diagnosis of exclusion. A working knowledge of identifiable PIDDs is essential in both recognizing when to suspect immunodeficiency and making a diagnosis.