MICI 2100 Lecture Notes - Lecture 10: White Blood Cells (Album), Red Blood Cell, Adaptive Immune System
2 Nov 2018
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MICI 2100 – Lecture 10 October 11, 2018
Different immune cells have specific and important
roles. In the picture, the red cells are red blood
cells. The white blood cells are shown in purple;
The ones with polymorphal nuclei are neutrophils,
a type of granulocytes. The lymphocytes are
circular, completely purple.
The Blood and Lymphatic Systems
• 0.1 percent of blood cells are leukocytes.
o Includes phagocytes and lymphocytes
o These are also known as ‘white blood cells’
• Whole blood is composed of plasma and cells.
o Plasma contains proteins and other solutes.
Serum – is the portion of blood that is not cells or
clotting proteins
The proteins in the blood includes antibodies as
well as antimicrobial proteins.
Red blood cells consists of the majority of the
blood. Lymphocytes have a huge nucleus to
cytoplasm ratio. Neutrophil have multi-lobe
nucleus and is also a phagocytes and granulocytes.
The granules insides are crucial for the function of
the cell; contains proteins that can be digestive or
cytokines that are released and lead to increase
immune response. Monocytes are precursors for
macrophages and dendritic cells.
Leukocytes Production and Diversity
• Leukocytes are nucleated white blood cells.
• Lymphocytes are specialized leukocytes; two types are involved exclusively in adaptive immune
response.
o B cells: originate and mature in the bone marrow
o T cells: originate in bone marrow, but mature in thymus
• Bone marrow and thymus are primary lymphoid organs (where the white blood cell matures).
In the blood, the cells that are enucleated are the red blood cells/ platelets. Lymphocyte is a type of
leukocytes. The two types of lymphocytes, B and T cells, are what constitutes the adaptive immune
system. The thymus is located just above the heart and atrophy with age.
There are 3 types of lymphoid organs: primary, secondary, and tertiary.
Hematopoiesis
Hematopoiesis – is the developmental pathway governing all blood cells
Everything originates from the bone marrow. The most important prime cell is called the hematopoietic
stem cell. This is a self-renewing cell in the bone marrow; some of its daughter cells start to
differentiation.
Differentiation – is the process where one cell transforms into another cell
Stem cell gives rise to all other types of cell. The differentiated versions are the functional cells of the
immune system.
The two main separation that can occur from a hematopoietic stem cells are the myeloid arm and the
lymphoid arm.
On the left hand side, the myeloid precursor give rise to everything called the granulocytes, which are
all involved in the natural innate immunity. A lot of these are phagocytes; neutrophils and
macrophages. Dendritic cells also gobble up things. Dendritic cells and macrophages capture, process
and present antigen to the immune system. They tell the adaptive immune system what they should be
reacting towards because these are sensory cells. The monocyte gives rise to dendritic cell and
macrophage. As well myeloid precursor can differentiate into granulocyte precursor, which can
differentiate into neutrophil and mast cells.
The lymphoid precursor splits into the lineage that would give rise to B cells and one that would give
rise T cells and NK cells. T cells are involved in adaptive immunity. B cells are the only cells in the body
that can make antibodies. The resting B cells do not make antibodies, but once activated when the
antibodies on the surface see its cognate antigen (specific antigen), it would transform into a plasma
cell, which is the factory for antibodies. This all happens in the bone marrow. The lymphoid precursor
can also differentiate into natural killer cells or T cells. Both cell types are involved cell-mediated
immunity, which refers to the cells that can kill other cells.
NK cells and T cells share a lot of properties but they do not share a T cell receptor, which defines a T
cell. The T cells mature in the thymus and the NK cell, like B cells, mature in the bone marrow.
Leukocyte Production and Diversity
• Myeloid cells are derived from a myeloid precursor cell.
o Can be divided into two categories:
1. Antigen-presenting cells (APCs) recognizes, engulfs, process, and present antigens to
lymphocytes, specifically B cells and T cells.
(Ex. monocytes, macrophages, and dendritic cells)
2. Granulocytes contains toxins or enzymes that are released to kill target cells.
(Ex. neutrophils, basophils, eosinophils)
• Lymphoid stem cells produce T cells, B cells, NK cells, and NKT cells.
• Each (adaptive) lymphocyte produces an unique protein that interacts with a single antigen.
o T cells: T cell receptors (TCRs)
o B cells: Antibodies or immunoglobulins (Igs)
On the lymphoid side, the NKT cells are like hybrids of the NK and T cells. Like a T cell, NKT cell have T
cell receptor but it is different because the T cell receptor on T cells binds to peptides but the T cell
receptor on NKT cells binds to glycolipids.
Hematopoiesis
Hematopoiesis – is the formation and development of both red
blood cells (erythrocytes) and white blood cells
(leukocytes)
1. White blood cells
• Granulocytes -> Granulopoiesis (Neutrophils,
eosinophils, basophils)
• Mast cells
• Monocytes -> Monocytopoiesis (Monocytes,
macrophages, dendritic cells)
• Lymphocytes -> Lymphopoiesis (T cells, B cells, NK
cells, NKT cells)
2. Red blood cells -> Erythropoiesis
3. Platelets -> Thrombopoiesis
All of the above are generated from hematopoietic stem cells in the bone marrow.
In adult, hematopoiesis happens in larger bones, especially the long bones but that wanes by late 20s.
Hematopoiesis continues on in the cranium, pelvis, sternum, ribs and vertebra. In the fetus,
hematopoiesis starts in the yolk sac and the organs, liver and spleen, take over. By 4 months on, the
bones start to take over the task.
Which of the following correctly describes a hematopoietic pathway?
A. Stem cell -> myeloid precursor -> T cell
B. Stem cell -> myeloid precursr -> B cell
C. T cell -> myeloid precursor -> stem cell
D. Mast cell -> myeloid precursor -> stem cell
E. Stem cell -> lymphoid precursor -> dendritic
cell
F. None of the above ****
