Vertebrate Immune Cells (Part-II)

Immunophenotyping

• A lab technique

• Used to identify and classify cells

• Based on the type of protein (markers) found on their surface

• Helps scientists tell different kinds of blood or immune cells apart

• Often using fluorescent tags and flow cytometry

Fluorescent tags

• Special dyes or molecules that glow under certain light.

• Scientists attach them to specific protein or cell parts

• So the labelled cells can be easily seen

• And measured under a microscope or by machines like flow cytometers.

Flow cytometry

• A lab technique

• Passes 1000s of cells one by one

• Through a laser beam

• Measures each cell’s size, shape, and the fluorescent tags attached

• Helping identify different cell types quickly and accurately.

CD34

• A protein

• Found on the surface of stem and early blood forming cells

• Often used to identify hematopoietic stem and progenitor cells

• inside the bone marrow or blood samples

CD45

• A protein

• Found on the most white blood cells

• Helps controlling how these cells send and receive signals

• Used as a marker to confirm that a cell belongs to the immune system

Lineage-negative (Lin-)

• Indicates that a cell does not have the surface markers typical of mature blood cells

• Shows that the cell is still in an early, undifferentiated stage (like a hematopoietic stem cell or a progenitor cell)

Proerythroblast

• 1st stage of the RBC formation

• A large cell

• Has a big round nucleus

• Has dark-blue cytoplasm

• Shows that it’s still very active in making proteins

• for hemoglobin production

Basophilic Erythroblast

• 2nd stage of the RBC formation

• Cell becomes smaller but

• The cytoplasm is dark blue

• Because cytoplasm is full of RNA for making hemoglobin

• Nucleus starts to get denser

Polychromatic Erythroblast

• 3rd stage of the RBC formation

• “Cell is in the middle of maturing”

• Cytoplasm turns grayish or purplish

• Because now it contains both RNA and red hemoglobin

• Nucleus becomes smaller and darker

Orthochromatic Erythroblast

• Almost final stage of the RBC formation

• Cytoplasm looks mostly pink due to lots of hemoglobin

• Nucleus is very small and ready to be pushed out of the cell

Cytokines

• Small signaling proteins

• Released by immune cells to communicate with each other

• Control how strong or weak the immune response is

• (Calling other cells to fight infection, reduce inflammation, or promote healing)

Protein

• A large molecule

• Made up of smaller units (Amino acids)

• Does most of the work in the body

• Building structures

• Catalyzing

• Sending signals

• Repairing the body

Mucosal surface

• A soft and wet inner lining found in

• Mouth

• Nose

• Lungs

• Stomach

• Intensities

• Protects the body

• Helps absorb or release substances

Epithelial barrier

• A thin layer of tightly joined cells

• Covers body surfaces (like skins or inside of the organs)

• Acts as a protective wall

• Keeping harmful substances out and allowing needed materials to pass through

Innate Lymphoid Cells (ILCs)

• Immune cells found in nearly all tissues, especially at mucosal surfaces

• Maintain the epithelial barrier

• Regulate the immune responses

Th1 cells

• A subtype of Lymphocytes T-cells

• Helps fighting bacteria viruses and bacteria living inside cells.

• Release cytokines like IFN-gamma

• To activate macrophages and promote cell-mediated immunity

CD8+ T cells

• Also called “Cytotoxic T cells

• Directly kill infected or cancerous cells

• By releasing toxic molecules

• Like perforin and granzymes

Interleukin-15 (IL-15)

• A cytokine

• Helps NK cells & CD8+ T cells survive and multiply

• Essential for maintaining a long-term immune protection

Interleukin-12 (IL-12)

• A cytokine

• Made by immune cells like macrophages

• Stimulates the growth and activation of Th1 cells, NK cells, and ILCs to boost defense against intracellular infections

Interleukin-18 (IL-18)

• A cytokine

• Works with IL-12

• To increase IFN-gamma production

• Strengthening the immune response against viruses and bacteria.

NK1.1

• A surface protein

• Found on NK cells

• And some ILC1s in mice

• Helps in identifying these cells

• Plays a role in activating immune functions

NKp46

• A receptor

• Found on NK cells and ILC1s

• Helps them recognize and destroy

• virus-infected cells/abnormal cells

• Part of the NCR family

Natural Cytotoxicity Receptor

Fullform of NCR

T-bet

• A transcription factor

• Controls the Th1 cells and ILC1s

• It turns on genes needed for IFN-gamma production

• And for strong antiviral defense.

Interferon-gamma (IFN-gamma)

• A powerful cytokine

• Made by NK cells, Th1 cells, and ILCs

• Activates macrophages

• Enhances antigen presentation

• Helps eliminate viruses and intracellular bacteria.

CD127 (IL-7Rα)

• A receptor subunit

• for interleukin-7

• Found on T-cells and ILCs

• Helps cells survive and maintain their functions

• By promoting growth and metabolism

Transcription Factor Eomes (Eomesodermin)

• A protein

• Regulates gene expressions in NK cells and CD8+ T cells

• Supports the ability of these cells to produce cytotoxic molecules

• And destroy infected cells

CD49a

• A cell adhesion molecule

• Helps immune cells to attach to tissues

• In ILC1s,

• marks tissue-resident cells that stay in organs like the liver and gut.

CD122 (IL-2Rβ)

• A receptor component for IL-2 and IL-15

• Important for the growth and activity of NK cells, CD8+ T cells, and ILC1s

Ly49

• A family of receptors found in

• on mouse NK cells

• that detect MHC class I molecules

• on target cells

• They help NK cells decide whether to attack or spare a cell.

Killer-cell Immunoglobulin-like Receptors

• Human equivalents of Ly49 receptors

• Detect MHC class I molecules

• Activates macrophages

• Control NK cell activation or inhibition

• to prevent damage of healthy cells

MHC class I

• Proteins found on nearly all body cells

• Display small pieces of internal proteins to immune cells

• They help the immune system recognize infected or abnormal cells.

Cytotoxic molecules

Substance made by killer immune cells that can destroy infected or cancerous cells.

Perforin

• A cytotoxic molecule

• A protein

• Released by NK cells and CD8+ cells

• That create pores in target cell membranes, allowing the other toxic molecules

• to enter and kill the cell

Granzyme B

• A cytotoxic molecule

• An enzyme

• Enters target cells through pores and

• Triggers cell death by breaking down vital proteins

• Inside the infected or cancerous cells.

ILC1

• ILC type to help fight viruses and intracellular bacteria’s

• Belong in the group 1 with NK cells

• Doesn’t have antigen receptors (allowing it respond quickly but non-specifically)

• Produces IFN-gamma and depends on the transcription factor T-bet

• Activated by IL-12, IL-15, and IL-18

• Found mostly at mucosal surfaces to protect epithelial barriers

• Lacks cytotoxic molecules like perforin and granzyme B.