Immunology Lecture 4 LO.pdf

Describe the types of blood cells that make up the immune system and outline the main events that occur during hematopoiesis, the process that gives rise to immune cells pluripotent stem cells (aka hematopoietic stem cells (HSCs)) Erythropoietin (EPO) initiates the erythroid series, which begins wit...

Describe the types of blood cells that make up the immune system and outline the main events that occur during hematopoiesis, the process that gives rise to immune cells pluripotent stem cells (aka hematopoietic stem cells (HSCs)) Erythropoietin (EPO) initiates the erythroid series, which begins with formation of the proerythroblast and ends with the mature erythrocyte (RBC) Granulocyte-macrophage colony stimulating factor (GM-CSF) triggers formation of the myeloblast, which will give rise to 4 of the 5 white blood cell lines: colony stimulating factor (G-CSF) in the presence of granulocytes - myeloblasts become neutrophils. colony stimulating factor (M-CSF) In the presence of monoblast – the monoblast gives rise to the monocyte. Blood cells are first made in the embryonic yolk sac and subsequently in the embryonic liver and spleen. Common myeloid Progenitor: 1. EPO -> Proerythroblast -> Erythrocyte 2. GM-CSF -> Myeloblast -> Big 3 granulocytes a. IL-3 i. Basophil b. IL-5 i. Eosinophil c. G-CSF i. Neutrophil 3. GM-CSF -> Monoblast -> M-CSF -> Agranulocyte Monocyte  a. M-CSF i. Monocyte ii. Differentiates into Macrophage and Osteoclast Common Lymphoid Progenitor 1. IL-7 -> Lymphoblast -> Agranulocyte Lymphocyte a. T Cells b. B Cells i. B cells give rise to Plasma cells Type 1 immunity protects against intracellular microbes through activation of mononuclear phagocytes; mediate autoimmune Type 3 immunity activate 3 immunity activates mononuclear phagocytes but also recruits neutrophils and induces epithelial antimicrobial responses, thus protecting against extracellular bacteria and fungi; mediate autoimmune Describe the function & role of each immune cell & be able to identify them based on generalized picture, description of function, and/or histology White blood cells: Presence/absence of granules in cytoplasm of cells (histological) Granulocytes: granules in cytoplasm - Neutrophil, Eosinophil, Basophil Agranulocytes: no granules in cytoplasm - Monocyte, lymphocyte Mast Cells: involved in immune response to parasitic worms & allergies Monocyte/Macrophages: Phagocytic cells. Monocytes travel in blood and invade tissues to become macrophages (agranulocytes) Thrombocytes (platelets): cell fragments formed from megakaryocytes. Important in hemostasis Dendritic cells: activates T cells to initiate adaptive immune response Erythrocytes: red blood cells (not a white blood cell)- oxygen delivery to tissues Degranulation - cellular process that releases antimicrobial cytotoxic or other molecules from secretory vesicles called granules found inside some cells Function Key Mechanisms Abundance Cell Type Neutrophil Most abundant Anti-bacterial Phagocytosis, degranulation, respiratory burst Eosinophil Degranulation, Less abundant Anti-worm respiratory burst, phagocytosis Basophil Allergic Reactions Degranulation Least abundant Be able to define key clinical terminology (e.g., leukocytosis, leukopenia, etc.) and diagnose it in blood work CD8+ Cytotoxic T cell- responsible for killing virus-infected cell CD4+ Helper T cell- direct immune response, aid in macrophage activation Tregs- act to suppress immune response, maintaining homeostasis & self-tolerance Th17- responsible to mount immune response against extracellular bacteria & fungi; role in autoimmune B Cells - One of the two main classes of lymphocytes responsible for adaptive immunity > plasma cells Dedicated to synthesizing (making) immunoglobulins in the form of cell-surface antigen receptors (B cell receptors) & antibodies, also a professional APC Plasma Cells - Terminally differentiated B lymphocyte that synthesize and secrete antibodies Leukocytes: White blood cells Leukopenia: low total WBC count Leukocytosis: high total WBC count Leukemia: cancer of blood (bone marrow and peripheral blood) Lymphocytes: subtype of Leukocytes, includes B cells & T cells Lymphoma: cancer of lymphoid tissue (e.g., lymph nodes) Lymphocytosis: high numbers lymphocytes Lymphopenia: low numbers of lymphocytes Suffix philia: Increased numbers Suffix “penia”: decreased numbers Front: Neutrophils Back:  Function: First responders to infection, phagocytosis & killing of microorganisms Histology: Multi-lobed nucleus (3-5 lobes) with pale granules. Identification: produced in BM, Segmented nucleus, acute inflammation/WBC. Front: Eosinophils Back: Function: Combat parasitic/worm infections, contribute to allergic reactions by releasing toxic substances and histamine. Histology: Bi-lobed nucleus with large, red-orange granules. Identification: mature in BM, enter tissue, Bilobed nucleus with prominent reddish granules. Front: Basophils Back: Function: Involved in allergic responses, release histamine and heparin, NO phago. Histology: Bi-lobed or S-shaped nucleus obscured by dark granules. Identification: Deep purple or blue granules that may obscure the nucleus. Front: Mast Cells Back: Function: Involved in allergic responses, wound healing, and defense against pathogens. Release histamine and other mediators during allergic reactions. Histology: Large cells with a round or oval nucleus, cytoplasm filled with large, dark purple granules. Identification: Cells with prominent dark granules, balloon shaped, leave BM and mature in the tissues such as skin and mucosa. Front: Monocytes Back: Function: Precursors to macrophages and dendritic cells; perform phagocytosis. Histology: Large cells with a kidney-shaped nucleus and pale cytoplasm. Identification: Large cells with an indented nucleus, often found in the bloodstream. Front: Macrophages Back: Function: Phagocytosis of pathogens and dead cells, long life, APC. Histology: Large cells with an irregularly shaped nucleus and abundant cytoplasm. Identification: Irregularly shaped cells, often found in tissues like the lung or liver. Front: Dendritic Cells Back: Function: Antigen-presenting cells that activate T cells and initiate adaptive immunity. Capture via phagocytosis and macropinocytosis Histology: Cells with branched, dendrite-like extensions. Identification: Cells with long extensions, found in tissues like the skin. Front: Lymphocytes Back: Function: Central to adaptive immunity; includes T cells, B cells, and NK cells. Histology: Small cells with a large, round nucleus and scant cytoplasm. Identification: Small, round cells with minimal cytoplasm. Front: T Cells Back: Function: Includes Helper T Cells (CD4+), Cytotoxic T Cells (CD8+), and Regulatory T Cells. Histology: Difficult to distinguish from B cells without markers. Identification: originate in BM, develop in thymus, activated in lymph nodes or spleen. Front: B Cells Back: Function: Produce antibodies, present antigens, differentiate into plasma cells. APC Histology: Difficult to distinguish from T cells without markers. Identification: Similar to other lymphocytes; plasma cells have more cytoplasm and a "clock-face" nucleus. Front: Natural Killer (NK) Cells Back: Function: Destroy virally infected and tumor cells without prior sensitization. Both innate and adaptive immunity Histology: Larger than other lymphocytes with more cytoplasm. Identification: Slightly larger lymphocytes with visible granules. Front: Plasma Cells Back: Function: Specialized B cells that secrete large amounts of antibodies. Histology: Eccentric nucleus with a "clock-face" chromatin pattern, abundant basophilic cytoplasm. Identification: Cells with an eccentric nucleus and abundant cytoplasm, often seen in chronic inflammation.