Binding site: corresponding area of ​​peripheral lymphoid organs

The contact is short-lived and reversible, mainly completed by adhesion molecules (LFA-1, CD2, etc.) on the surface of T cells and corresponding ligands (ICAM-1, LFA-3, etc.) on the surface of APC

Purpose: Provide antigen opportunities for TCR-specific contact

Specific binding→CD3 molecules specifically recognize signals into cells→LFA-1 conformation changes and enhances affinity with ICAM-1

Dual recognition: TCR-antigenic peptide/MHC I/II

Core receptor: CD4-MHC II; CD8-MHC I

Tyrosine phosphorylation in ITAM in the cytoplasmic domain of the CD3 molecule: transducing T cell activation signals

The most important molecular pairs: CD80/86 (APC)/CD28 (T cells) and other pairs promote the expression of IL-2, IL-2R, and BCL-XL, and participate in T cell proliferation and anti-apoptosis

IL-1, IL-2, IL-6

CD4 T cells

CD8 T cells

Produce different types of cytokines, which act extensively on neighboring cells

auxiliary humoral immune response

Involved in hypersensitivity inflammation

Tregs effect

Th17 effect

Effect of Tfh

CTL highly expresses adhesion molecules and specifically binds TCR

A tight, narrow space is formed between the target cell's pMHC, CTL and the target cell.

The subcellular structures in the CTL cytoplasm are rearranged and aggregated to facilitate granule exocytosis.

Cell lysis: perforin

Apoptosis: granzyme, Fas/FasL pathway, TNF-α