Lecture 2: Principles of Innate Immunity (09/10/2024)

Lecture 2 Principles of Innate Immunity 09/10/2024  Cells of the immune system Learning Principles of innate immunity Objectives Types of pathogens Lines of Defense Immune System...

Lecture 2 Principles of Innate Immunity 09/10/2024  Cells of the immune system Learning Principles of innate immunity Objectives Types of pathogens Lines of Defense Immune System Second line of defense Specific immunity Innate Adap0ve Immunity Immunity First line of defense Non-specific immunity Humoral Cell-mediated Immunity Immunity B cell-mediated via Igs T cell-mediated Innate vs. Adaptive Immunity There are two general types of immunity: 1. Innate Immunity (Prior knowledge/training is not necessary) Present at birth Provides an immediate (within hours) response to a broad range of pathogens - Non-Specific No memory 2. Adaptive Immunity (Prior knowledge/training is necessary) Not present at birth. It is learned It takes time to develop as specific to a pathogen Hallmarks – ability to learn, adapt and remember (memory) Humoral vs. Cell-Mediated Immunity More on Sep. 19th! Created with BioRender.com Protection against pathogens relies on several levels of defense Physical barrier Chemical barrier Sensor Cells Fig. 1.5 Physical and Chemical barriers Epithelial surfaces AnBmicrobial pepBdes Fig. 2.5 Commensals Mucus and mucins in diseases of the intestinal and respiratory tracts Journal of Internal Medicine, Volume: 285, Issue: 5, Pages: 479-490, First published: 08 April 2019, DOI: (10.1111/joim.12910) Lysozyme digests the cell walls of Gram- positive and Gram-negative bacteria Lysozyme (yellow, lower panels) creates a defect in the peptidoglycan layer and exposes the underlying cell membrane to other antimicrobial agents. Lysozyme is more effective against Gram-positive bacteria because of the relatively greater accessibility of the peptidoglycan. Fig. 2.9 Defensins are amphipathic peptides that disrupt the cell membranes of microbes Positively charged defensins interact with the charged surface of the cell membrane and become inserted in the lipid bilayer (center panel), which leads to the formation of pores and a loss of membrane integrity Fig. 2.10 Quiz time! The collec7on of microorganisms that normally inhabit our body is known as…? Answer: Microbiota (or commensals) Quiz time! Which of these is an antimicrobial peptide 1. Defensin 2. Cathelicidin 3. Histatin 4. All of the above ✅ Protection against pathogens relies on several levels of defense Physical barrier Chemical barrier Sensor Cells Fig. 1.5 The origins of vertebrate immune cells Cellular and chemical barriers Innate Immunity Secreted proteins Both innate and adaptive immune responses depend on Cells the activities of leukocytes Immune system White blood Secreted proteins cells (WBCs) or leukocytes Adap7ve Immunity Cells The cells of the innate immune system Innate Immune Cells Granulocytes Agranulocytes Innate Neutrophils Eosinophils Monocytes Dendritic Cells Lymphocytes Basophils Mast Cells Dendritic Cells NK Cells Macrophages ILCs The cells of the innate immune system Granulocytes: Neutrophils, Basophils, Eosinophils, Mast cells Myeloid antigen-presenting cells (APCs) – Monocytes, Macrophages, Dendritic Cells Innate Lymphocytes – Natural Killer (NK) cells, Innate Lymphoid Cells (ILCs) Macrophages, granulocytes, and dendritic cells make up the three classes of phagocytes in the immune system. Cells of adaptive immune system Almost all cells of the immune system are derived from haematopoietic stem cells in the bone marrow, where many of them develop and mature. Myeloid lineage Most* Innate cells aka HSCs Lymphoid lineage Most* Adaptive cells The myeloid lineage comprise most of the cells of innate immune system The innate immune cells - Granulocytes Myeloid lineage Contain granules in their cytoplasm; these are membrane organelle containing important proteins and chemicals pivotal to an immune response Neutrophils – predominant, >50% of circulating leukocytes (WBCs) Eosinophils – 1-3%. Important in parasitic infections Basophils –