Immunology Lecture - T-cell Differentiation (Part 5)

Thymus

Site of T-cell Differentiation

Double-Negative Stage

T-cells lack CD4 and CD8 markers

Double-Positive Stage

T-cells express both CD4+ and CD8+

Positive Selection

T-cell must recognize self-MHC molecules

Negative selection

Eliminates T-cell that bind self-antigens

Mature T-cells

T-cells that survived the positive selection becoming single-positive cells

CD4 or CD8

Mature T-cells lose these surface markers

CD4+ T-helper cells

Recognize MHC Class II molecules then activates immune responses

Th1 Cells

Produce IFN-y TNF-b to protect against intracellular pathogens

Th2 Cells

Produce IL-4, IL-5, IL-10, IL-13 → Help B-cells in antibody production (against extracellular pathogens)

T-regulatory cells

Suppress immune responses against self-antigens → Prevent autoimmunity

CD8+ T-cytotoxic cells

Recognize MHC Class I molecules → Destroy virus-infected and cancerous cells

CD25

Key marker of Activated T cells

Natural Killer Cells

this cell does not express markers of T-cells or B-cells

Spleen
Circulating blood

NK cells are found in these organ and area of the body

Natural killer Cells

Kills virus-infected and cancerous cells without prior exposure

CD16 and CD56

Surface markers on NK cells

IgG

NK cells binds to this antibody

No CD56 and High CD16

This NK cell subtype has higher cytotoxic activity

High CD56 and No CD16

this NK cell subtype produce more cytokines

Perforins
Granzymes

NK cell triggers release of these substance

Antibody-Dependent Cell Cytotoxicity

NK cells target and kill antibody-coated cells.

CD16
IgG

Antibody-Dependent Cell Cytotoxicity is mediated by this surface marker and antibody