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.

Invertebrates Invertebrate immune systems have nonspecific response mechanisms, but they lack pathogen-specific defense responses. innate immune system, also known as non-specific immune system (respond in a generic way)

2 types of invertebrate defenses Insects' exoskeleton made mostly of a polysaccharide called chitin, serves as an effective barrier against microbes Phagocytosis is used to engulf bacteria cells

Plants Innate Response 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.

Vertebrate nonspecific Immunity The epithelial surfaces form a physical barrier. gastrointestinal and respiratory tract, movement due to peristalsis or cilia helps remove infectious agents; and mucus traps infectious agents The gut can prevent the colonization of pathogenic bacteria by secreting toxic substances The flushing action of tears and saliva helps prevent infection of the eyes and mouth. Inflammation is one of the first responses of the immune system to infection or irritation. Ex: histamine

All white blood cells (WBC) are known as leukocytes All white blood cells (WBC) are known as leukocytes. Leukocytes are different from other cells of the body in that they are not tightly associated with a particular organ or tissue; thus, they function similar to independent, single-celled organisms. Leukocytes are able to move freely and interact with and capture cellular debris, foreign particles, or invading microorganisms. Unlike many other cells in the body, most innate immune leukocytes cannot divide or reproduce on their own, but are the products of multipotent hematopoietic stem cells present in the bone marrow. The innate leukocytes include: Natural killer cells, mast cells, eosinophils, basophils; and the phagocytic cells including macrophagess, neutrophilss and dendritic cells, and function within the immune system by identifying and eliminating pathogens that might cause infection.

All white blood cells (WBC) are known as leukocytes All white blood cells (WBC) are known as leukocytes. Leukocytes are different from other cells of the body in that they are not tightly associated with a particular organ or tissue; thus, they function similar to independent, single-celled organisms. Leukocytes are able to move freely and interact with and capture cellular debris, foreign parti es, or invading microorganisms. Unlike many other cells in the body, most innate immune leukocytes cannot divide or reproduce on their own, but are the products of multipotent hematopoietic stem cells present in the bone marrow. The innate leukocytes include: Natural killer cells, mast cells, eosinophils, basophils; and the phagocytic cells including macrophagess, neutrophilss and dendritic cells, and function within the immune system by identifying and eliminating pathogens that might cause infection.

The mammalian immune system includes two types of specific responses: cell mediated and humoral Cell-mediated immunity is an immune response that does not involve antibodies but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes(a type of white blood cell), and the release of various cytokines in response to an antigen Cell-mediated immunity is directed primarily at microbes that survive in phagocytes and microbes that infect non-phagocytic cells. It is most effective in removing virus-infected cells, but also participates in defending against fungi, protozoans, cancers, and intracellular bacteria.

Humoral In the humoral response, B cells, a type of lymphocytic white blood cell, produce antibodies against specific antigens. Humoral immunity is so named because it involves substances found in the humours, or body fluids. The principal function of B cells is to make antibodies

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. What are memory T-cells? Memory T-cells are derived from normal T-cells that have learned how to overcome an invader by ‘remembering’ the strategy used to defeat previous infections. (adaptive immunity)