Dendritic Cells Connect Innate and Specific Immunity
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Dendritic Cells Connect Innate and Specific Immunity
Historically, human immune mechanisms have been divided into two categories for the purposes of study. Some anti-pathogen mechanisms are considered innate and non-specific, while others are considered acquired, adaptive, and specific. The non-specific, innate defenses include physical barriers like the epidermis and mucosae, bactericidal external secretions (i.e. lysozyme in tears), physiological mechanisms such as intestinal transport and urinary flushing, the acidity of the gastric secretions, and non-immune phagocytosis. These mechanisms can be effective against a wide variety of generic pathogens and are present at birth. Adaptive immunity includes those processes that occur in response to a particular infection. These mechanisms are specific to the invading pathogen and characteristically exhibit immunological "memory" with respect to that pathogen. Specific Immunity involves a polyclonal expansion of specific populations of B and T lymphocytes carrying selected receptors able to respond to particular non-self molecules or parts of molecules, some of which persist upon elimination of the original offending antigens, ready to mount a more vigorous response in the event that the original pathogen is encountered again. As with most biological systems, innate and specific immunity do not operate as separate entities, but are intimately connected at the level of the antigen-presenting cell, particularly the dendritic cell...