A client with acquired immune deficiency syndrome (AIDS) and Pneumocystis jiroveci pneumonia has a CD4+ T cell count of 200 cells/mm³ (20%). The client asks the nurse why they have these recurring massive infections. Which pathophysiological mechanism should the nurse describe in response to this client's question? Reference Range: T-helper CD4 cells [600 to 1500 cells/mm³ (60 to 75%)]

The humoral immune response lacks B cells that form antibodies and opportunistic infections result.

Inadequate numbers of T lymphocytes are available to initiate cellular immunity and macrophages.

Bone marrow suppression of white blood cells causes insufficient cells to phagocytize organisms.

Exposure to multiple environmental infectious agents overburdens the immune system until it fails.