Immunology Lecture - Hematopoiesis, Phagocytosis, and Inflammation (Part 1)

Hematopoiesis

Formation and development of all types of blood cells from their parental precursors.

Yolk sac
Primitive RBC

Mesoblastic period’s primary hematopietic organ and cells formed at this stage

Liver
Spleen

Hepatic period’s primary hematopietic organ and secondary hematopoetic organ

Bone marrow
RBC and WBC

Myeloid period primary hematopietic organ and cells formed at this stage

0 to 2 months

Mesoblastic period starts at this months

2 to 5 months

Hepatic Period starts at this months

6 months

Myeloid Period starts at this months

2 to 5 months

Spleen blood production starts at this months

4th month of childhood

Thymus aids at blood production at this months

4th month of adulthood

Lymph nodes aids at blood production at this months

Pleuripotent Stem Cell

Self-renewing stem cell that differentiates into blood cells.

Granulocytes
Eryhtrocytes
Monocytes
Megakaryocytes

Myeloid series

Precursord T-cells and B-cells

Lymphoid series

Phagocytosis

The ability of granulocytes and macrophages to engulf and digest foreign substances.

Chemotaxis
Adherence
Engulfment
Digestion
Excytosis

Stages of Phagocytosis

Chemotaxis

Stage of Phagocytosis where Migration of phagocytes to the site of injury.

Adherence

Stage of Phagocytosis where Phagocyte binds to the pathogen.

Engulfment

Stage of Phagocytosis where Phagocyte engulfs the pathogen

Digestion

Stage of Phagocytosis where the pathogen is broke down 

Exocytosis

Stage of Phagocytosis where Waste materials are expelled.

Antigen presentation

Stage of Phagocytosis where Fragments of the pathogen are presented to activate the immune response.

Diapedesis

Ability of neutrophils and monocytes to move from blood circulation to tissues.

Neutrophils

Actively motile, reaches injury site faster, short lifespan (5 days), forms small pus cells after engulfment

Monocytes

Slower-moving, longer lifespan (months), forms large pus cells after engulfment.

Chemoattractants

Chemical signals that guide cells to the site of injury

Chemotaxin

Specific chemical that guides immune cells towards the site of injury, infection, or inflammation

Positive movement

Type of movement induced by chemotaxins where phagocytes migrate towards the site of injury

Negative Movement

Type of movement induced by chemotaxins where phagocytes migrate away from the site of injury

Chemotactic Response

Change in the direction of movement of a motile cell in response to chemotaxins.

Opsonization

Process where opsonins coat a pathogen to enhance phagocytosis.

Antibodies
C3 molecule

Type of Opsonins

FC receptor
Complement Receptor

Cell surface receptors

C3 molecule

Molecule that initiates the complement cascade for increased phagocytosis

Leukocyte Adhesion Cascade

The process of white blood cells being recruited to the site of injury, infection, or inflammation

Capture Adhesion Molecules
Chemicals: P-selectin, L-selectin

Factors Influencing Leukocyte Adhesion

Phagosome

Pathogen + Phagocyte =

Phagolysosome

Lysosome + Phagosome =

Lysozyme
Myeloperoxidase

WBC’s Primary granules

Lactoferrin

WBC’s Secondary Granules (Specific Granules) contains

Capsases

WBC’s Tertiary Granules contains

Chronic Granulomatous Disease

A congenital disorder where WBCs engulf pathogens but cannot kill them due to defective oxygen metabolism.

Coagulase

Protein enzyme that converts fibrinogen to fibrin.

Staphylothrombin

Enables protease enzymes to convert fibrinogen to fibrin, leading to blood clotting.

Staphylococcus aureus

Bacteria that coats itself with fibrin, resisting phagocytosis and increasing virulence.

Superoxide
Hydrogen Peroxide

These substances when mixed together degradation of bacterial membrane will occur

H2
Lysozymes
Bactericidal proteins

These three helps to degrade bacterial membrane

Inflammation

The body's general reaction to tissue injury or pathogen invasion.

Prostaglandins and Leukotrienes

Vasoactive factors that increase vascular permeability and induces leukocyte migration

C3b and C5a
Leukocyte secretions

Chemotactic Factors that enhance neutrophil migration

Acute inflammation

Rapid onset, peaks at 16–48 hours, and resolves quickly.

Chronic inflmmation

Prolonged and may cause tissue damage and loss of function.