Final answer:
The process by which cells become clumped when mixed with a specific antiserum is called agglutination. Antibodies attach to antigens on the cells' surface, causing them to stick together and form clumps. This is an important defense mechanism of the immune system.
Step-by-step explanation:
The process by which cells become clumped when mixed with a specific antiserum, such as in the case of agglutination, is a phenomenon in immunology. Antibodies attach to antigens on the surface of cells, causing them to stick together and form clumps. This can happen when an immune individual's serum is mixed with a culture of the same type of bacteria, resulting in the clumping of the bacteria. For example, when serum from an immune individual is mixed with a fresh culture of bacteria of the same species, the antibodies in the serum bind to the bacteria's antigens, causing them to clump together. However, when a different bacterial species is used, this clumping does not occur. Overall, this process of cells becoming clumped with the help of specific antibodies is an important defense mechanism by which the immune system can neutralize foreign antigens and prevent the spread of infection.