CH7 Development of T lymphocytes

T-cells are not thymus-dependent lymphocytes (T/F)

False (Development requires migration to the thymus)

Thymocytes

immature T cells

Thymic stroma

network of epithelial cells in the thymus

Thymic anlage

The tissue formed from cell movements that will develop into the mature thymus

Hassall’s corpuscles are often seen in thymus medulla. (T/F)

True

Macrophages and dendritic cells-

-are responsible for removal of defective thymocytes.

CD34

• In all hematopoietic progenitor cells.

  – This protein is removed from thymocytes in the thymus

CD2

• adhesion molecule for retention in thymuS

CD127

• (= IL-7 receptor)

• cytokine receptor for signals to T-cells

  – IL-7 (interleukin 7) is a cytokine produced by thymic stromal cells

double-negative (or DN) thymocytes

• immature thymocytes do not produce CD4 or CD8 proteins during early development

• TCR receptor genes (for a and b proteins, or g and d proteins) begin to undergo genetic recombination

double-positive (or Dt) thymocytes

Gene rearrangements to form TCRs; cells have both CD4 and CD8

• Notch 1 proteins

thymocytes act as a gene regulatory proteins to control production of appropriate thymocyte proteins

IF functional proteins are produced (either y:d proteins, or beta proteins), the cells will not

then express CD4 and CD8 proteins. (T/F)

False

If successful production of a beta chain protein inactivates the delta chain, this commits the thymocyte to producing alpha:beta T-cell receptor (T/F)

True

positive selection for T cells

• The T-cell receptor proteins are screened for binding to MHC receptor proteins on thymic epithelial cells

• (~2%) survival rate for T cells.

• occurs in the cortex

Cells that bind tightly to self-antigens-

-are signaled for apoptosis. Moderate binding, antigen lives

autoimmune regulator (AIRE

transcription factor that activates gene expression and protein synthesis for MHC I antigens

derived from these self proteins (e.g. insulin) – this

allows for immunotolerance of antigens from

phagocytized cells.