Immune Response Regulation and Innate vs Adaptive Immunity

Study Notes

Immune responses must be sufficient to protect against invading pathogens, with prompt and specific down-regulation when the foreign material is no longer present.
Hypersensitivity occurs when immune responses are not properly regulated, leading to excessive or inappropriate responses and disease.

The immune system is divided into two major functional categories: innate and adaptive immunity.
Innate immune mechanisms provide the first line of defense against infectious diseases, existing from birth and comprising physical and biochemical barriers.
Innate mechanisms include anatomic barriers (skin, mucous membranes), physiologic barriers (temperature, low pH), phagocytic cells (neutrophils, macrophages), and inflammatory responses.
Innate mechanisms trigger the cells involved in adaptive immunity to combat specific organisms.

Innate immunity: rapid response (minutes to hours), nonspecific, no memory, and no increase in response to secondary exposure.
Adaptive immunity: slow response (days to weeks), specific, memory, and maturation of secondary response to reexposure.

The immune system is a network of protective barriers, organs, cells, and molecules.
Central lymphoid organs (bone marrow, thymus, spleen, and lymph nodes) contain high levels of lymphocytes and manage interactions.
Cells are available to be called into action at short notice and can be found within every major organ and tissue.

Anatomic and physiologic barriers: physical barriers to limit the entry, spread, and replication of pathogens.
Inflammatory mediators: direct lysis of pathogens or infected cells, activation of other immune components, and bacterial destruction.
Cellular components: phagocytosis and intracellular destruction of microorganisms, presentation of foreign antigens to lymphocytes.