What infections are complement deficiencies associated with?

Complement deficiencies are primarily associated with an increased susceptibility to infections caused by encapsulated bacteria, particularly those of the Neisseria genus, such as Neisseria meningitidis and Neisseria gonorrhoeae. The complement system plays a crucial role in the immune response, facilitating opsonization and clearance of pathogens. It enhances the ability of antibodies and phagocytic cells to clear microbes and promote inflammation.

Individuals with complement deficiencies, especially those affecting the classical pathway (which includes components that are crucial for responding to Neisseria species), are at a higher risk for invasive meningococcal disease. This is due to the inability to effectively opsonize these organisms for phagocytosis and the impaired ability to generate the membrane attack complex that would normally lyse Neisseria bacteria.

Other types of infections, like those caused by fungi or other viral and bacterial pathogens, are not as specifically linked to complement deficiencies. While individuals with impaired complement function may have a broader susceptibility to various infections, recurrent infections with Neisseria species are notably highlighted due to their unique reliance on complement-mediated immune responses for clearance.