Final answer:
B-cell maturational arrest can lead to agammaglobulinemia, or XLA, due to mutations in the BTK gene leading to insufficient immunoglobulin production, making patients prone to recurrent infections from specific extracellular bacteria.
Step-by-step explanation:
B-cell maturational arrest can lead to a condition known as agammaglobulinemia, specifically X-linked agammaglobulinemia (XLA). This occurs due to a mutation in the BTK gene that encodes the Bruton tyrosine kinase enzyme. This enzyme is critical for B-cell maturation and differentiation beyond the pre-B-cell stage, which is essential for immunoglobulin production. Without functional BTK, patients are unable to produce antibodies and are therefore susceptible to recurrent infections, particularly from extracellular pathogens that cause pyogenic infections. Examples of these pathogens include Haemophilus influenzae, Streptococcus pneumoniae, S. pyogenes, and S. aureus. However, since cell-mediated immunity remains intact, these patients are not significantly vulnerable to viral or intracellular pathogens.
B cells normally undergo a selective process in the bone marrow which includes both positive selection, to ensure functionality of antigen-binding receptors, and negative selection, to eliminate self-reacting B cells and prevent autoimmunity. Those B cells that pass this selection phase then travel to the spleen for their final maturation stages, where they become naïve mature B cells, ready to be activated during an immune response.