Which statement best describes an immune response that occurs in invertebrates? a)cytotoxic t cells recognize infected cells and then bind to and destroy them. b)enzymes such as lysozyme break down the cell walls of harmful bacteria. c) t cells produce antibodies when a foreign antigen is recognized. d)natural killer cells engulf infected cells, destroying them via phagocytosis.

Ans.

Lysozymes are hydrolytic enzymes, synthesized and secreted by various organisms as a defense mechanism against bacterial infections. Invertebrates show type-i lysozymes (invertebrate lysozyme).

Lysozyme kills gram-positive bacteria by breaking bacterial cell walls as it prevents polymerization of components, required for cell wall synthesis. Invertebrates do not have immune cells, such as T cell, B cells, and natural killer cells.

Thus, the correct answer is 'option b). enzymes such as lysozyme break down the cell walls of harmful bacteria.'