What immunological feature is characteristic of patients with Bruton's agammaglobulinemia?

Bruton's agammaglobulinemia, also known as X-linked agammaglobulinemia (XLA), is characterized by a severe deficiency of mature B cells due to a mutation in the BTK gene, which is crucial for B cell development. As a result, individuals with this condition have significantly reduced levels of immunoglobulins (antibodies) and a near-total absence of B cells in their peripheral blood.

The absence of functional B cells leads to the failure of the development of germinal centers in lymphoid tissues, including the tonsils. Consequently, individuals often exhibit absent or significantly reduced tonsils and other lymphoid tissues, which are normally populated by B cells. This loss of lymphoid tissue is a key immunological feature of Bruton's agammaglobulinemia.

In contrast, the other options present features that do not align with the immunological profile of this condition. For instance, IgA levels would be low rather than high, plasma cells would not be elevated due to the lack of B cell maturation and differentiation, and patients would show a reduced B cell count rather than a normal one. Thus, the characteristic absent tonsils and lymphoid tissue correctly identifies the hallmark of Bruton's ag