The immune system: basis of so much health and disease: 3. adaptive immunity Crispian Scully Eleni A Georgakopoulou Yazan Hassona Dental Update 2024 44:4, 707-709.
The immune system is the body's primary defence mechanism against infections, and disturbances in the system can cause disease if the system fails in defence functions (in immunocompromised people), or if the activity is detrimental to the host (as in auto-immune and auto-inflammatory states). A healthy immune system is also essential to normal health of dental and oral tissues. This series presents the basics for the understanding of the immune system; this article covers adaptive immunity.
Clinical Relevance: Dental clinicians need a basic understanding of the immune system as it underlies health and disease.
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At times when ‘smart pathogens’ pass undetected through the innate immune barriers, the immune system reacts in a more complex defensive way, by launching the adaptive (acquired) immune response. The innate immune response (Article 2) calls the adaptive immune responses into play, and both then work together to eliminate pathogens (Figure 1). The adaptive immune responses react specifically and develop memory for subsequent exposure to the same pathogen.
There are two broad classes of adaptive immune responses; antibody responses (humoral) and cell-mediated responses.
The main cells that mediate adaptive immunity are white blood cells (leukocytes) termed immunocytes – mainly lymphocytes:
B-cells and T-cells derive their names from the organs in which they develop:
Despite their different origins, both B- and T-cells develop from the same pluripotential bone marrow haemopoietic stem cell (Figure 2).
The bone marrow and the thymus are thus referred to as central (primary) lymphoid organs because they are sites where lymphocytes develop from precursor cells (Figure 3).
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