The immune system: basis of so much health and disease: 4. immunocytes Crispian Scully Eleni A Georgakopoulou Yazan Hassona Dental Update 2024 44:5, 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 cells of the immune system (immunocytes).
Clinical Relevance: Modern dental clinicians need a basic understanding of the immune system as it underlies health and disease.
Article
The immune system employs various cells to protect humans from pathogens. All immune cells (immunocytes) are bone marrow-derived white blood cells (leukocytes) which have specialized functions (Article 1) and can be functionally categorized into three main groups:
T-lymphocytes are produced in the bone marrow from the pluripotential bone marrow haemopoietic stem cell and migrate to the thymus (hence the T) where they complete their development (Article 3). T-cells are particularly important in acquired immunity against:
T-cells are also involved in mediating immunological processes such as:
These functions are mediated by different subsets of T-lymphocytes distinguished by unique surface markers known as cluster of differentiation (CD); these surface markers also mediate antigen recognition, and interactions between T-cells and APCs by functioning as cell surface receptors (known as T-cell receptors, TCRs).
T-cells recognize antigens through their TCR. Some T-cells develop TCRs as they mature and these have an affinity to bind to MHC Class II antigens, and will become T-helper (Th) cells (identified by their expression of CD4 (CD4+ cells). Other T-cells as they mature develop TCRs that have an affinity to bind to major histocompatibility complex (MHC) Class I antigens and will become T-cytotoxic (Tc) cells identified by their expression of CD8 (CD8+ cells). Other groups of T-cells include gamma-delta T-cells (γδ T-cells) and regulatory T-cells (T-regs) (Table 1).
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