The Immune System
Structures of the Immune System
• Innate Immunity consists of defenses that are always active against infection, but do not
have the ability to target specific invaders. Nonspecific Immunity
• Adaptive or Specific Immunity: defenses that target a specific pathogen. Is slower to act,
but maintains a memory of an infection so that it can more quickly attack subsequent
infections
Anatomy
• Bone Marrow produces all leukocytes that participate in the immune system. Are
created through hematopoiesis.
• Spleen: location of blood storage and activation of B-cells, which turn into plasma cells
to produce antibodies as part of adaptive immunity.
o When B-cells leave the bone marrow, they are mature but naïve since they have
not been exposed to an antigen.
o These antibodies dissolve in the blood and not in the cell, because of this, they
are a division of adaptive immunity called humoral immunity.
• Thymus: location of maturation for T-cells.
o Agents of cell-mediated immunity since the T-cells coordinate the immune
system and directly kill virally infected cells.
• Lymph Nodes: Provide a place for immune cells to communicate and mount an attack
o B-cells can also be activated here.
• Gut-associated lymphoid tissue (GALT): immune tissue found close to the digestive
system. Have a higher chance of potential invasion.
o Tonsils, adenoids in the head, Peyer’s patches in the small intestine, and
lymphoid aggregates in the appendix.
• Leukocytes produced through hematopoiesis and can be divided into granulocytes and
agranulocytes. Granules contain toxic enzymes and chemicals and are effective against
bacterial, fungal and parasitic pathogens.
o Granulocytes: include neutrophils, eosinophils and basophils
o Agranulocytes: Lymphocytes which are responsible for antibody production,
immune system modulation and targeted killed of infected cells. And Monocytes
which are phagocytic cell in the blood.
▪ Monocytes become macrophages in tissue and some names are specific
to the tissue they reside in. (microglia for CNS, Langerhans cells in the
skin, Osteoclasts in bone)
Classification
• Nonspecific immune response includes antimicrobial molecules, phagocytes. Also
triggers an inflammatory response which triggers an influx of immune cells through the
increased blood flow.
• Specific Immune Response is adaptive and can be further divided:
o Humoral immunity: driven by B-cells and antibodies
o Cell-mediated immunity: provided by T-cells.
