Defence mechanisms against bacterial pathogens include A - VCE - SSCE Biology - Question 15 - 2013 - Paper 1

Histamines are chemicals released during immune responses, particularly in allergic reactions and inflammation. While histamines play a role in the immune system, they are not directly involved in neutralising bacterial pathogens. Thus, this defense mechanism is also incorrect.

Complement proteins are part of the immune system that aids in the destruction of pathogens, including bacteria. They can lyse bacterial cells and opsonise them for easier phagocytosis. Hence, this is a correct mechanism of defense against bacterial pathogens.

Cytotoxic T cells primarily target infected or cancerous cells rather than agglutinating bacteria. Agglutination refers to the clumping of particles, generally involving antibodies, not cytotoxic T cells. Therefore, this defense mechanism is not applicable to bacterial pathogens.