This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
Patients with C5 through C9 complement deficiencies would be most likely to have which of the following infections? 
Select and explain. 
A. AIDS, B. Meningococcal infection, C. Pneumococcal infection, D. Giardiasis
B: Meningococcal infection
Answer: B: Meningococcal infection 
Explanation: Patients with complement deficiencies such as C5 through C9, which form the membrane attack complex (MAC), are predisposed to disseminated meningococcal disease. These patients may also be susceptible to gonococcal infection. There appears to be no disposition to AIDS or to fungal, parasitic, or pneumococcal infections.