Cellular and Molecular Components of the Immune System PDF

Module 03: Hematology and Immunology Cellular & Molecular Components of the Immune System Anna Kristina M. Gutierrez-Rubio, MD, FPCP, DPRA, FACR | September 19, 2023 | Onsite TABLE OF CONTENTS Learning Objectives 1 B. Antigen-Recognizing 10 I. Cell...

Module 03: Hematology and Immunology Cellular & Molecular Components of the Immune System Anna Kristina M. Gutierrez-Rubio, MD, FPCP, DPRA, FACR | September 19, 2023 | Onsite TABLE OF CONTENTS Learning Objectives 1 B. Antigen-Recognizing 10 I. Cellular Components 1 Molecules A. Classifications of 1 C. Pattern Recognition 16 WBCs Molecules of Innate B. Phagocytes 3 Immune System C. Antigen-Presenting 7 D. Complement 16 Cells E. Cytokines 17 D. Lymphocytes 8 III. Summary & Keypoints 19 II. Molecular Components 10 Review Questions 19 A. Basic Definition 10 References 20 Appendix 21 LEARNING OBJECTIVES 1. Describe the cellular and molecular components of the immune system 2. Detail the function of the molecules involved in immunity Figure 1. Location of Cells in the Immune System OVERVIEW Anatomic organization and ability to circulate allow our immune The body needs to defend itself against a diverse set of harmful system to: pathogens/agents including: ﹣ Respond rapidly to small numbers of many different ﹣ Single-celled organisms (bacteria, single-celled eukaryotes) microbes that may be introduced at any site in the body ﹣ Multicellular organisms (worms & some fungi) ﹣ Maintain a small number of specialized cells that recognize ﹣ Viruses and respond to any one antigen ﹣ Altered self-cells (cancer & other autoimmune diseases) ﹣ Locate and destroy microbes at sites that are distant from These agents employ a variety of mechanisms that harm the the immune response was induced body (e.g., intracellular and extracellular attack, release of toxins, Capacity to optimally perform its protective functions depends etc.) on: Likewise, the body has evolved an extensive and collaborative ﹣ The remarkably rapid and varied responses of immune cells system to defend itself ﹣ The way these cells are organized in lymphoid tissues The immune system has many players that include cells, ﹣ Their ability to migrate from one tissue to another antibodies, other proteins, and chemicals that work together A. CLASSIFICATION OF LEUKOCYTES I. CELLULAR COMPONENTS OF THE IMMUNE SYSTEM Leukocytes = White Blood Cells (WBC) Location of the cells in the immune system: Considered the main cells of the immune system ﹣ Circulating in the blood and lymph Mobile units of the body's protective system ▪ Lymph: Interstitial fluid that drains into lymphatic vessels Formed partially in the bone marrow and partially in the lymph and enters the blood. It contains components of the tissue immune system (Abbas et al., 2021) ﹣ Note: Generated, however, in the bone marrow ▪ Lymphatic system: system of vessels parallel to blood Unlike Red Blood Cells, they do not carry oxygen vessels that carries lymph to and from tissues (e.g., Used for protection against infection lymphocytes) Outline of WBC Types ▪ Connecting all of them are the lymph nodes and major lymphatic organs (e.g., spleen and tonsils) ﹣ Anatomically defined collections in lymphoid organs (See: Anatomy and functions of Lymphoid Tissues) ﹣ Scattered cells in virtually all tissues Figure 2. Major Lineages of White Blood Cells There are several types of white blood cells, each with their own morphology and immune function TG12 | Abad, Alagar, Alonzo, Aoanan, Generoso, Lim, Negre, Paguia, Salmingo, Santos, A., Tecson, Zabat YL5 03.05 1 of 22 CG3 | Bambalan, Galvez, Jamoralin, Miguel, Mirabueno, Peroja, Salvador, Santos E., Santos J., Santos R., Uy, Zamora  Table 2. Lifespan of White Blood Cells Nice! In blood In tissues → The following numbers enclosed in the parentheses pertain to 4-5 days the numbers seen in Figure 2 A few hours in Granulocytes 4-8 hours seriously ﹣ Granulocytes injured/infected ▪ Polymorphonuclear neutrophils (7) tissue ▪ Polymorphonuclear eosinophils (10) Months (as tissue Monocyte 10-20 hours ▪ Polymorphonuclear basophils (12) macrophages) ﹣ Monocytes (15) Lymphocytes Weeks or months ▪ Eventually develop into macrophages (16) Platelets Replaced every 10 days ﹣ Lymphocytes ▪ B-cells → Will mature into plasma cells Granulocytes ▪ T-cells ﹣ Granular in appearance ▪ Innate lymphoid cells (ILCs) ﹣ Granulocytes are also called “polys” or “PMNs” − Natural killer cells (NK cells) (polymorphonuclear cells) because multiple nuclei are present ﹣ Lifespan after being released from the bone marrow: Classification of WBCs according to their Genesis ▪ 4-8 hours (circulating in the blood) ▪ Then another 4-5 days (in the tissues) ﹣ In severe tissue infection, lifespan is shortened to a few hours because the granulocytes proceed even more rapidly to the infected area to perform their function ﹣ In the process, these granulocytes get destroyed Monocytes ﹣ Short transit time: 10-20 hours in the blood before wandering through the capillary membranes into the tissues ﹣ Once in the tissues, they swell to much larger sizes to become tissue macrophages ▪ In this form, they can live for months unless destroyed while performing any function, specifically phagocytosis ▪ These tissue macrophages are the basis of the tissue macrophage system, which provides continuing defense Figure 3. Genesis of Red and White Blood Cells against infection Location: Bone Marrow Lymphocytes All WBCs are formed from the same Pluripotent Hematopoietic ﹣ Enter the circulatory system continually, along with drainage Stem Cells (PHSC) as erythrocytes of lymph from the lymph nodes and other lymphoid tissue PHSC differentiates into the different types of committed ﹣ After a few hours, they pass out of the blood back into the precursor stem cells tissues by diapedesis ﹣ Common Myeloid Progenitor (CMP): differentiates into ﹣ Lymphocytes then re-enter the lymph and return to the blood erythrocytes, megakaryocytes, and the myelocyte series again and again ﹣ Common Lymphoid Progenitor (CLP): differentiates into B- ▪ Thus, lymphocytes are constantly circulating throughout and T-lymphocytes the body Two major lineages of WBCs are formed: ﹣ Lifespan: weeks or months, depending on the body's need ﹣ Myelocytic Lineage or Myeloid Line for these cells ▪ Beginning with the Myeloblast (see 1 in Figure 2) Platelets ▪ Consists of the monocytes and the granulocytes ﹣ Hemostasis ﹣ Lymphocytic Lineage or Lymphoid Line ﹣ Replaced once every 10 days ▪ Beginning with the Lymphoblast ﹣ About 30,000 platelets are formed each day for each Table 1. Normal Blood Cell Counts microliter of blood Mean Number per (mm3) Normal Range White blood cells 7400 4500-11,000/mm3 (leukocytes) Neutrophils 4400 40-60% 1-4% Eosinophils 200 Basophils 40