Which process involves antibodies cross-linking cells or particles into large aggregates?

• A. Opsonization
• B. Neutralization
• C. Complement activation
• D. Agglutination

Answer: (D)

Verified step by step guidance

1. Understand the definition of each process: Opsonization is the coating of pathogens with antibodies to enhance phagocytosis; Neutralization involves antibodies binding to toxins or viruses to block their activity; Complement activation triggers a cascade leading to pathogen lysis; Agglutination is the clumping of cells or particles caused by antibodies cross-linking them.
2. Focus on the key phrase 'antibodies cross-linking cells or particles into large aggregates' which describes a physical clumping effect.
3. Recall that agglutination specifically refers to this clumping process where antibodies bind multiple antigens on different cells or particles, causing them to stick together.
4. Compare this with other options: Opsonization and neutralization do not cause visible clumping, and complement activation leads to cell lysis rather than aggregation.
5. Conclude that the process involving antibodies cross-linking cells or particles into large aggregates is agglutination.