Which characteristic indicates B cell deficiency?

The indication of B cell deficiency is closely linked to the inability to produce antibodies. B cells are a crucial component of the adaptive immune system, responsible for recognizing specific antigens and generating antibodies to neutralize them. When there is a deficiency in B cells, the body's ability to mount an effective immune response to pathogens—particularly extracellular organisms such as bacteria—significantly diminishes. This lack of antibody production can lead to recurrent infections, especially with encapsulated organisms, underscoring the importance of B cells in maintaining immunity.

In contrast, the inability to fight off cancer cells is generally associated with T cell deficiencies or dysfunction rather than specifically with B cell deficiencies. Granulomas are often linked to certain chronic inflammatory conditions or infections, suggesting more complex immunological issues and not directly related to B cell function. The increased incidence of anemia may result from various causes, including chronic disease or nutritional deficiencies, but is not a hallmark of B cell deficiency specifically. Thus, the hallmark characteristic of B cell deficiency is the inability to produce antibodies, confirming the correctness of the chosen answer.