Lecture 31 Flashcards
Plasma in the blood
Plasma (55%)**: Plasma is the liquid portion of blood, making up about 55% of its volume. It contains water, proteins (including antibodies or immunoglobulins), other solutes such as electrolytes, hormones, and waste products.
Formed elements in the blood
Platelets**: Platelets are small cell fragments involved in blood clotting and wound healing.
Formed Elements (45%)**: Formed elements are cellular components suspended in plasma, including white blood cells (leukocytes) and red blood cells.
White Blood Cells (Leukocytes)**: These are cells of the immune system involved in defending the body against infections and foreign substances.
Red Blood Cells**: Also known as erythrocytes, these cells are responsible for transporting oxygen from the lungs to the body’s tissues and removing carbon dioxide from tissues to the lungs for exhalation.
In summary, blood is a complex fluid that carries out various essential functions in the body, including oxygen transport, immune defense, and clotting. Its composition reflects its multifaceted role in maintaining homeostasis and supporting bodily functions.
Bone marrow
Bone marrow stem cells = source of blood cells
(hematopoiesis)
Blood Cell Lineages Myeloid
• Myeloid → red blood cells (erythrocytes)
granulocytes, monocytes, dendritic cells, platelets (innate immune cells)
Blood Cell Lineages Lymphoid
Lymphoid →
B and T lymphocytes (adaptive immune cells)
Granulocytes in Blood
Neutrophils - 75% of all leukocytes, highly phagocytic “eat and kill” - numbers in blood increase during infection
Granulocytes circulate in the blood and can move into tissue during inflammation
Granulocytes in Tissue
Mast cells
• Mast cells line mucosal surfaces (not found in blood)
• Release granules (in dark purple) that attract white blood cells to areas of tissue damage
Phagocytic cells, Monocytes and Macrophages
• Monocytes present in blood → low phagocytosis
• Leave blood - develop into macrophages in tissues e.g. spleen, liver → high phagocytosis
Macrophages
Macrophage become resident (sessile) or move through tissues (migratory)
3 important functions
1. Phagocytosis (professional eaters)
2. Release of chemical messengers
3. Show information about pathogenic microbes to T cells (linking innate and adaptive immunity)
Dendritic cells: linking innate and adaptive immune responses
• Found in low numbers blood and all tissues in contact with the environment
• Phagocytic
• Most important cell type to help trigger adaptive immune responses
How do cells of the immune system move around the body?
- Cells are carried in the blood and in the lymph
• Cells can leave blood to enter tissues
• Lymph in tissues collects into lymphatic vessels. These drain lymph into lymph nodes.
How innate cells recognise pathogens. Pathogen-associated molecular patterns
(PAMPS) examples
Virus
-Envelope
-Nucleocapsid
-Nucleic acid
COMMON BUILDING BLOCKS OF VIRUSES:
Nucleic acid: ssRNA, dRNA
Bacterium
-Capsule
-Cell wall
-Cell membrane
-Nucleic acid
-Flagella
COMMON BUILDING BLOCKS OF BACTERIA:
Cell wall: lipopolysaccharide (LPS)/ endotoxins, lipoteichoic acid
Flagella: flagellin
Nucleic acid: unmethylated CpG DNA
Pattern Recognition Receptors
Pattern Recognition Receptors (PRRs) are a crucial component of the innate immune system, responsible for detecting various conserved molecular patterns associated with pathogens
Pattern Recognition Receptors (PRRs) are a crucial component of the innate immune system, responsible for detecting various conserved molecular patterns associated with pathogens. Here’s a breakdown of their key components and functions:
Bacterial Cell Wall Components**: PRRs can recognize molecular components of bacterial cell walls, such as lipopolysaccharides (LPS), lipoteichoic acid, and peptidoglycans.
Yeast Cell Wall Components**: Similarly, PRRs can detect molecular patterns present in yeast cell walls, such as β-glucans and mannans.
Toll-like Receptors (TLRs)**: TLRs are a family of PRRs that are located on the cell surface or within endosomes. They play a central role in recognizing a wide range of pathogen-associated molecular patterns, including bacterial and viral components.
Phagolysosome**: After pathogens are engulfed by phagocytic cells, they are enclosed within a vesicle called a phagosome. This phagosome fuses with lysosomes to form a phagolysosome, where pathogens are degraded and destroyed.
Cell Membrane**: Some PRRs, like TLRs, are located on the cell membrane, where they can detect extracellular pathogens or pathogen-derived molecules.
Cell Signaling to Regulate Gene Transcription**: Upon activation by pathogen recognition, PRRs initiate intracellular signaling cascades that lead to the activation of transcription factors. These transcription factors then regulate the expression of genes involved in the immune response, including genes encoding cytokines, chemokines, and antimicrobial peptides.
Bacterial and Viral Nucleic Acids**: PRRs can also recognize nucleic acid sequences that are characteristic of bacterial and viral genomes, such as unmethylated CpG motifs in bacterial DNA or double-stranded RNA in viral genomes.
Nucleus and Cytoplasm**: Signaling pathways activated by PRRs lead to the translocation of transcription factors into the nucleus, where they modulate gene expression. These pathways can originate from both the cell membrane-bound receptors (e.g., TLRs) and intracellular receptors (e.g., RIG-I-like receptors for viral RNA detection).
FEVER/PYREXIA
- Abnormally high temperature > 37°C
• Re-setting of thermostat (hypothalamus)
• Pyrogens - released by cells of the immune system
• Phagocytes produce the chemical messenger and pyrogen interleukin-1 (IL-1) after ingesting bacteria
• Why might fever be useful? - decrease phagocytosis→ decrease IL-1 → decrease temperature
3 layers of immune defense
- Physical & Chemical Barriers (skin, mucosal membranes)
- The Innate Immune System
- The Adaptive Immune System
