Week 2. Red Blood Cells Flashcards
How does mean cell volume change in diseases?
Decreases in iron deficiency
Increases in B12 anaemia
what are 3 useful red blood cell indices?
Haemoglobin (g/dL)
Mean cell volume (fl)
Red cell count (10^12/L)
Why are reticulocytes called that?
Because of their reticular (mesh-like) network of ribosomal RNA that becomes visible under a microscope with certain stains like-> new methylene blue.
RBC lifespan?
120 days
Romanowsky results for red blood cell?
Pink.
Strength of colour shows how much haemoglobin is in the cell. So faint colour= not much Hb
Size of RBC
- 5um diameter.
2. 0um depth
Hereditary spherocytosis
Most common HA in northern europe. Defects in proteins involved in vertical interactions between membrane cytoskeleton and lipid bilayer. Cell becomes spherical. Die prematurely.
Clinical features and treatments of hereditary spherocytosis
Anaemia. Jaundice. Increased bilirubin because increased rbc destruction.
Splenomegaly-> spleen gets bigger.
Splenectomy last resort.
Stages of erythropoiesis?
Hemocytoblast (stem cell) Proerythroblast (committed cell) (now into developmental pathway) Early erythroblast (ribosome synthesis) Late erythroblast Normoblast (haemoglobin accumulation and ejects nucleus) Reticulocyte Erythrocyte!
Describe the peripheral proteins of the rbc membrane?
- spectrin (alpha and beta. alpha=globular part, beta=chain)
- Protein 4.1 links to cytochrome c
- protein 4.2 links to band 3 via ankyrin and to spectrin.
- Ankyrin links band 3 to 4.3 and then spectrin
- Actin at 4.1 spectrin and 4.2 spectrin links.
When does polychromasia occur?
When the immature reticulocytes are released, resulting in greyish blue coloured cells.
Colour is due to ribosomes still left on the immature RBC. Ribosomal RNA left in reticulocyte.
Reticulocytes under romanowsky stain
Appear slightly bluer than RBCs because of ribosomal rna still left inside.
What is the width of capillaries and red blood cells?
Capillaries are 2-3um wide.
Red blood cells are 7-8 um diameter.
So the red blood cell needs to be tough and flexible
How does plasmodium falciparum invade red blood cells?
Extra reading
1982 study.
When glycophorin B is removed by trypsin treatment RBCs are partly resistant to plasmodium falciparum invasion. When glycoprotein A-> completely resistant.
More modern studies show there are multiple pathways of invasion.
What functions does the rbc membrane have?
- separates cell contents from plasma
- maintains biconcave disc shape
- regulates intracellular cation conc.
- Interface for membrane-bound cell receptors
What is the composition of the rbc membrane?
50% protein
42% lipis
8% carbohydrate
How many RBC membrane proteins are there?
What roles do they have?
Currently more than 50 known proteins. Around 25 of these carry the various blood group antigens
roles= transport (25% of membrane) e.g. band 3, aquaporin
cell adhesion
structural role
Most common phospholipids?
Phosphotidylcholine (PC) 30%
Phosphotidylethanolamine (PE) 28%
Sphingomyelin 25%
Can rbcs make lipids from scratch?
Mature rbc cant make lipids de novo.
There are lipid renewal pathways and cholesterol content of the membrane is regulated by exchange between plasma cholesterol and membrane cholesterol.
Maintains equilibrium. Found to happen more rapidly in old than young rats. May be due to larger pool of free cholesterol in old rats. [Malhotra and Kritchevsky]
Examples of membrane proteins for:
- Transport
- cell adhesion
- Structural role
- transport- Band3, aquaporin 1 (water), glut1 (glucose and L-dehydroascorbic acid), RhAG (gas probably co2)
- Cell adhesion- ICAM 4 (interacts with integrins), BCAM (glycoprotein also known as Lu or laminin-binding protein
- Structural role-
Ankyrin-based macromolecular complex- proteins linking the bilayer to the membrane skeleton through the interaction of their cytoplasmic domains with Ankyrin.
Band 3- assembles glycolytic enzymes
duffy protein (extra)
What system destroys rbs normally?
The reticuloendothelial system (RES)
How do monocytes contribute to the reticuloendothelial system?
Monocytes leave the blood stream and enter tissue and specialise. Can break down rbcs in other organs than spleen e.g. when no spleen body adapts- macrophages in bone marrow. Kupffer cells in liver. (name for monocytes in these places)
What is a haemolytic disorder?
What is compensated haemolysis?
When increased haemolysis.
The body tries to make more RBCs to compensate.
Get haemolytic anaemia when the RBCs are broken down faster than they are made.
What happens when rbcs are about 120 days old?
They burst in narrow spleen channels.
Macrophages in the spleen and liver digest the cell components here. Convert haem to bilirubin. Becomes bile and then faeces. Haem and globin recycled.