Final answer:
Protective antibodies neutralize pathogens by blocking the ability to bind to host cell receptors, and promote passive immunity by being transferred from one individual to another, while marking pathogens for destruction by immune cells.
Step-by-step explanation:
Protective Antibodies and Their Role
Protective antibodies play a crucial role in our immune response by targeting extracellular pathogens and neutralizing them. This neutralization blocks the pathogen's ability to bind to host cell receptors. A classic example of antibody involvement in protection is through the use of vaccines which promote the production of these antibodies, specifically IgA for pathogens entering through mucous membranes like influenza.
Another important function of antibodies is the provision of passive immunity, which can be natural, as seen with breastfeeding, or through transfusions where antibodies are transferred from an immune person to a nonimmune individual. This confers temporary immunity and protection against infection.
Moreover, antibodies have a role in marking pathogens for destruction by the immune system. They can create complexes with the antigens, stimulating the complement system and enhancing phagocytosis. This function prevents infection by various mechanisms, including preventing the adherence of pathogens to host cells.
Neutralizing antibodies are essential in blocking key sites on a pathogen and preventing cellular infection. When antibodies attach to pathogens, they can be filtered by the spleen and subsequently eliminated.