Cells of the Immune System Flashcards
What is the root stemcell for all blood cells?
Pluripotent hematopoietic stem cell
Branches from pluripotent haematopoetic stem cells
Myeloid stem cells
Lymphoid stem cells
Dendritic Cells (via various intermediate cells)
Which cells are derived from myeloid stem cells?
Platelets RBCs Basophils Neutrophils Eosinophils Macrophages (monocytes)
Percursor cells for basophils and neurtrophils etc.
Myeloblast
Myeloid stem cells become:
Megakaryocytes that produce platelets Reticulocytes become: Red Blood Cells (RBCs) Promyelocytes become: Monocytes – Macrophages Neutrophils Eosinophils Mast Cells Basophils
Lymphoid Stem Cells travel to the thymus gland and differentiate into
B lymphocytes (B cells) (mature in the bone marrow) that differentiate into:
- Plasma Cells
- Memory B Cells
T lymphocytes (T cells) (mature in the thymus) that differentiate into:
- CD4 cells (T helper cells)
- CD8 cells (Cytotoxic T Cells)
Natural Killer Cells
Megakaryocytes
Large cells
Big lobulated nucleus
Produce platelets
Platelets are essential for blood clotting
Reticulocytes
Immature red blood cells
Remnant RNA material called reticulum in cytoplasm
Released from bone marrow
Normally 1% of red blood cells are reticulocytes
Higher percentage indicates rapid turnover of blood, such as in:
—Acute blood loss
—Haemolysis
Loose their reticulum after a few days – becoming:
RBCs
Contain large quantity of Hb
Lifespan of ~3months
Macrophages
Monocytes circulate the blood stream
Enter tissues and differentiate into macrophages
Live in most tissues in the body
Have “Toll-Like Receptors“
Recognise “Pathogen-associated molecular patterns” (PAMPs)
Kill pathogens and abnormal cells by phagocytosis
Release cytokines that initiate the inflammatory response
Activate the other cells of the immune system
Neutrophils
Circulate through the blood and lymphatic system
Migrate to areas of inflammation
Kill pathogens and abnormal cells by phagocytosis
Eosinophils
Important in responding to parasites
They normally sit waiting in tissues
Contain granules with:
==Proinflammatory cytokines
==Chemicals toxic to pathogens, such as “major basic protein“
They have two functions:
==Exocytosis of their granules
==Phagocytosis (but less than neutrophils and macrophages)
Mast Cells and Basophils
Mast cells are fixed in place in tissues
Basophils circulate through the blood
Contain cytoplasmic granules
Degranulation releases pro-inflammatory cytokines
B Lymphocytes
Also called B cells
Mature in the bone marrow
Cell surface lined with antibodies
Each B cell has a specific type of antibody for a specific antigen
There are millions of different possible antibodies and therefore
millions of different specific B cells
B cells can only recognise antigens that match their antibodies
Once activated B cells become either:
- Plasma cell – secrete antibodies (also called immunoglobulins)
- Memory B cell – await a later infection with the same pathogen
T Lymphocytes
Also called T cells
Pro-thymocytes leave the bone marrow and travel to the thymus gland
Mature in the thymus gland into T cells
Cell surface lined with T-cell receptors
Each T cell has a specific type of T-cell Receptor (TcR) for a specific antigen == CD4 cells have CD4 TcRs that recognise MHC class 2 receptors == CD8 cells have CD8 TcRs that recognise MHC class 1 receptors
CD4 cells become T-helper cells when activated
T-helper cells help other cells become activated, including CD8 cells
CD8 cells become cytotoxic T cells when activated
Cytotoxic T cells destroy infected cells via
Granule exocytosis causing destruction of the cell
Activating the Fas pathway causing cell apoptosis
