a short presentation on T-cells

1. T-Cells
Presented by: Arslan Amanat

2. Introduction
• A type of lymphocytes
• Most important white blood cells of immune system
• Play central role in Acquired (Adaptive) immunity
• Can be easily distinguished from other lymphocytes
due to presence of T-cell receptor(TCR) on their
surface

3. Introduction
• They are abbreviated as ‘T’ cells because
they mature in Thymus.
• On entering thymus they lack TCR
• Also lack other supporting surface receptors
• Upon exiting thymus they have a unique
TCR
• At this stage called mature naïve T-cells

4. Mechanism
• All T cells originate from haematopoietic
stem cells in the bone marrow.
• Haematopoietic progenitors from
haematopoietic stem cells populate the
thymus and expand by cell division to
generate a large population of immature
thymocytes.
• The earliest thymocytes express neither CD4
nor CD8, and are therefore classed as double-
negative (CD4−CD8−) cells.

5. Mechanism
• As they progress through their development,
they become double- positive thymocytes
(CD4+CD8+), and finally mature to single-
positive (CD4+CD8− or CD4−CD8+)
thymocytes that are then released from the
thymus to peripheral tissues.

6. Thymic Selection of T-cells
Three checkpoints;
1. Beta Selection
2. Positive Selection
3. Negative Selection