Essential Knowledge 2.D.4

Plants and animals have a variety of chemical defenses against infections that affect dynamic homeostasis.

Plants, invertebrates and vertebrates have multiple, nonspecific immune responses.

Examples:

• Invertebrate immune systems have nonspecific response mechanisms, but they lack pathogen-specific defense responses.
• Plant defenses against pathogens include molecular recognition systems with systemic responses; infection triggers chemical responses that destroy infected and adjacent cells, thus localizing the effects.
• Vertebrate immune systems have nonspecific and nonheritable defense mechanisms against pathogens.

Mammals use specific immune responses triggered by natural or artificial agents that disrupt dynamic homeostasis. The mammalian immune system includes two types of specific responses: cell mediated and humoral. In the cell-mediated response, cytotoxic T cells, a type of lymphocytic white blood cell, “target” intracellular pathogens when antigens are displayed on the outside of the cells. In the humoral response, B cells, a type of lymphocytic white blood cell, produce antibodies against specific antigens. Antigens are recognized by antibodies to the antigen. Antibodies are proteins produced by B cells, and each antibody is specific to a

particular antigen. A second exposure to an antigen results in a more rapid and enhanced

immune response.

Students should be able to:

LO 2.29 Create representations and models to describe immune responses.

LO 2.30 Create representations or models to describe nonspecific immune defenses in plants and animals.

LO 2.43 Connect the concept of cell communication to the functioning of the immune system.