Which of the following is NOT a type of pathogen?

Antibodies are not classified as pathogens; rather, they are components of the immune system. Their primary role is to identify and neutralize pathogens such as viruses, bacteria, and parasites. Antibodies are proteins produced by B cells in response to the presence of foreign invaders. They help the body recognize and combat infections, facilitating the immune response.

In contrast, viruses, bacteria, and parasites are all types of pathogens that can cause disease. Viruses are tiny infectious agents that replicate only inside the living cells of organisms. Bacteria are single-celled organisms that can be beneficial or harmful, depending on the type. Parasites are organisms that live on or in a host and benefit at the host's expense.

Recognizing that antibodies serve a protective function instead of being pathogens highlights the importance of their role in maintaining health and fighting infections.