immune

1. Immune cells , Receptors, and Markers:
White blood cells or leukocytes serve as defenders
against infection.
They move around the body via the lymphatic and
blood circulatory systems, and can leave and reenter the
circulation to move through body tissues.

2. N
Leukocytes are classified according to their morphology,
origin, and immunologic function into the following
groups:
1-Cells of Myeloid lineage:
A-Granular leukocytes: Neutrophils, Eosinophils, and
Basophils.
B-Agranular leukocytes:
Monocytes , and macrophages.
2-Cells of Lymphoid lineage:
A-Agranular leukocytes: T cell, B cell.
B-Granular leukocytes: NK cell.

3. Leukocytes and Immune system:
N

4. N
Cells of Myeloid lineage:
A-Granular leukocytes:
1-Neutrophils or polymorphonuclear cells:
-Form 60% of the peripheral blood leukocytes.
-Metamyelocyte , juvenile (band) form, Stab form, and
segmented (mature) form.
-Very effective at killing bacteria.
-Elevated number: mainly in acute bacteria infection.
2-Eosinophils:
-Eosin-loving granules.
-form 0-5% of WBCs.
-Activated due to parasitic helminthes infection.

5. N
3-Basophils:
-Acidic cytoplasmic granules contain histamine.
-Form 0-1% of WBCs.
-Activated due to allergic response.

6. N
B-Agranular leukocytes:
Monocytes , and macrophages:
-Monocytes in the circulation, and macrophage in the
tissues.
-5-7% of peripheral blood
leukocytes.
-Scavenger cells for innate
immunity.
-Antigen presenting cells
(APC).
-Macrophage markers:
CD14, CD40, CD11b

7. Cells of Lymphoid lineage:
A-Agranular leukocytes:
Lymphocytes:
- Immune system must be able to distinguish its own cells,
and organs (Self) from those of foreign origin (nonself).
- The innate immune cells depend on Pathogen
recognition receptors (PRRs).
-The adaptive immune cells utilizes somatically generated
epitope-specific T and B lymphocyte receptors.

8. N
According to type of receptor, and organs of differentiation
(where they undergo basic training), Lymphocytes are
classified into three groups:
1-Thymus-derived cells (T-Cells):
-Arise from Bone marrow as prothymocytes.
-Enter the circulation from Thymus.
-Identified by presence of CD3 complex (TCR).
-Two subsets:
- CD4⁺ T cells: Restricted to the recognition of
MHC class II Complexes.
- CD8 ⁺ T cells: Restricted to the recognition of
MHC class I complexes.

9. N
2-Bone marrow-derived cells (B-Cells):
-Remain and develop within bone marrow.
-The precursors of Ig-producing lymphocytes.
-Two types:
B cells:
-Arise from hematopoietic stem cells in B.M.
-Have two different lineages: B1, and B2.
-B1 present in respiratory &GIT Systems.
-B2 widely distributed in lymphoid organs and tissues.
-IgM and IgD present on both cells surface.
-Isotype switching is typical for B2 lineage.
-Markers : CD19, and CD20.

10. N
Plasma cells:
- Terminally differentiated B cells.
- Immunoglobulin producing cells.
3-Natural killer cells (NK-Cells):
-Forms 5-10% peripheral blood lymphocytes.
-Lack both T cell receptor and B cell receptor.
-Very active in killing of Virally infected cells and Tumor
cells.
-Carry two receptors: Killer activation and inhibition
receptors (KARs and KIR).

11. Immune cell(s) Receptors:
-A wide variety of immune system activities is initiated by
receptor-ligand interaction.
- Different intracellular signals are generated due to
activation of immune cell receptors.
-The immune cell receptors are classified into two types:
1-Preformed receptors:
A-Pattern recognition receptors:
: CRP, CD14,C3b and MBP; recognize pathogen
associated molecular patterns (PAMP).
B-Toll-like receptors:
Activated by binding to a PAMP.

12. Toll-like receptors and Recognition of PAMP:
n

13. N
C-The complement receptors:
-C3b fragments bind to its receptors on Phagocytes and
B lymphocytes.
D-The immunoglobulins Fc receptors:
-epitope-engaged antibodies are recognized by
phagocytic cells Fc
receptors.
-The Fc receptor that binds
IgE is the exception.

14. N
Examples on Immunoglobulin Fc receptors:
Immune cell Receptor Effector Function
Macrophage,
Neutrophils, and
Eosinophils.
FcγR I
FcαR I
-Uptake, and
Stimulation.
-Induction of Killing
Mast Cell
Basophils
FcεRI Degranulation.

15. N
E-The Natural Killer cell receptors:
1-Killer activation receptors (KARs):
-Recognize the presence of Stress-related molecules
(MICA and MICB) expressed by the unhealthy host
cells.
2-Killer inhibition receptors:
(KIRs):
-Recognize the presence of
MHC class I , which is
normally displayed on the
host cell surfaces.

16. N
2-Somatically generated receptors:
A-B cell receptors (BCR):
-Immunoglobulins serve as B-cell
receptors.
-Two Igα and Igβ chains initiate
intracellular signaling cascade;
due to binding of antibody to
its epitope.
B-T cell receptors (TCR):
-Cluster of differentiation 3 (CD3).
-Binds to MHC.
-CD4 and CD8 are co-receptors.