Basic Concepts in Immunology and Components of the Immune System
DOI:
https://doi.org/10.33687/ricosbiol.04.04.120Keywords:
Infection, pathogenicity, normal microbiota, innate immunity, adaptive immunity, (MALT), lactoferrin., lysozyme, , M cells, skin barrierAbstract
This chapter introduces the fundamental concepts of immunology, focusing on the relationship between infection and the host immune system. It defines key terms such as infection, pathogenicity, and normal microbiota, and classifies infections by localisation, incidence, etiology, and systematic site. The chapter then distinguishes between the two major branches of the immune system: nonspecific (innate) immunity and specific (adaptive) immunity. The cellular components—including lymphocytes (B cells, T cells, natural killer cells), mononuclear phagocytes, granulocytes, mast cells, and dendritic cells—are described in terms of their origin, maturation, and function. The primary lymphoid organs (bone marrow and thymus) and secondary lymphoid tissues (spleen, lymph nodes, and mucosa‑associated lymphoid tissue) are explained as sites of lymphocyte development and antigen encounter. Finally, the physical and mechanical barriers that constitute the first line of defence—skin, mucous membranes, and associated secretions—are reviewed, with special attention to the role of M cells in mucosal immunity. Together, these elements provide the foundation for understanding how the body recognises and defends against microbial invaders while maintaining self‑tolerance.
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References
Abouelhag, H. (2010). Basic immunology, MLT 360: Hand out 2010/2011 [Unpublished course handout].
Abbas, A. K., Lichtman, A. H., & Pillai, S. (2022). Cellular and molecular immunology (10th ed.). Elsevier.
Delves, P. J., Martin, S. J., Burton, D. R., & Roitt, I. M. (2023). Roitt's essential immunology (14th ed.). Wiley Blackwell.
Huang, Q., et al. (2023). Deciphering tumor infiltrating dendritic cells in the single cell era. Experimental Hematology & Oncology, 12(1), 45. https://doi.org/10.1186/s40164-023-00459-2
Murphy, K., Weaver, C., & Berg, L. (2022). Janeway's immunobiology (10th ed.). W.W. Norton & Company.
Nature Portfolio. (2024). Innate immunity. Nature. https://www.nature.com/subjects/innate-immunity
Punt, J., Stranford, S. A., Jones, P. P., & Owen, J. A. (2023). Kuby immunology (8th ed.). Macmillan Education.
Science Immunology. (2025). The multifunctional immune system. Science.
Shafqat, A., et al. (2023). How neutrophils shape the immune response: Reassessing their multifaceted role in health and disease. International Journal of Molecular Sciences, 24(24), 17583. https://doi.org/10.3390/ijms242417583
Wang, J., et al. (2024). Gut microbiota as a key regulator of intestinal mucosal immunity. Life Sciences, 345, 122612. https://doi.org/10.1016/j.lfs.2024.122612
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Data Availability Statement
The data supporting the conclusions of this review are derived from previously published studies, which are cited throughout the manuscript. Any aggregated datasets used for comparative analysis, if applicable, are available from the corresponding author upon reasonable request.
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Copyright (c) 2026 Abouelhag H. A.
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