Which group of infections are individuals with membrane attack complement (MAC) formation deficiency more susceptible to?

Individuals with membrane attack complex (MAC) formation deficiency have an increased susceptibility to Neisseria infections. The MAC is an important component of the complement system, which plays a critical role in the immune response by directly lysing certain bacteria, particularly Gram-negative bacteria like Neisseria species.

Neisseria meningitidis, the bacterium responsible for meningococcal disease, and Neisseria gonorrhoeae, which causes gonorrhea, are both particularly vulnerable to destruction by the MAC. When the formation of this complex is impaired, the body loses a key mechanism for combating these organisms, leading to increased risk of severe infections.

In contrast, other options may not be as closely associated with the MAC. For instance, streptococcal infections are typically dealt with by phagocytosis and other immune pathways, while viral infections are primarily managed by cellular immunity rather than the complement system. Fungal infections, although potentially influenced by complement, are generally less reliant on the specific mechanisms facilitated by the MAC compared to Neisseria. Therefore, the deficiency in MAC formation specifically heightens risks for infections caused by Neisseria.