Which of the following is NOT an effect of complement activation?

• A. Opsonization of pathogens
• B. Direct lysis of microbial cells
• C. Recruitment of inflammatory cells
• D. Stimulation of antibody production by B cells

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the role of the complement system in the immune response. The complement system is a group of proteins that, when activated, help clear pathogens through several mechanisms.
2. Step 2: Identify the known effects of complement activation: (a) Opsonization, which tags pathogens for phagocytosis; (b) Direct lysis of microbial cells via the membrane attack complex; (c) Recruitment of inflammatory cells by releasing chemoattractant molecules.
3. Step 3: Recognize that stimulation of antibody production by B cells is primarily a function of the adaptive immune system, specifically involving helper T cells and B cell activation, not a direct effect of complement activation.
4. Step 4: Compare each option to the known effects of complement activation and determine which one does not fit the complement system's functions.
5. Step 5: Conclude that 'Stimulation of antibody production by B cells' is NOT an effect of complement activation, as it involves a different immune pathway.