Immunology I -ch11

Flashcards reviewing antigen presentation to T lymphocytes, T cell activation, co-stimulation, and T cell apoptosis.

Dendritic cells (DC)

Antigen-presenting cells of the immune system born in the bone marrow that process and present antigens to CD4 T cells.

Co-stimulatory molecule

Surface molecule that helps in the activation of T cells by binding to its receptor on T-cells alongside the MHC complex.

Dendritic cells (DCs)

The most potent antigen-presenting cells due to efficient antigen presentation, activation of T Helper cells (CD4 T cells), and expression of co-stimulatory molecules (CD80, CD86).

Two-Signal Hypothesis

States that activation of a T cell requires two signals: Signal 1 from antigen-specific T cell receptor (TCR) and Signal 2 from antigen-independent co-stimulatory receptor.

Interaction of CD80 with CD28

Leads to enhanced T-cell activation when CD80 ligand interacts with the CD28 receptor.

Interaction of CD80 with CTLA-4

Inhibits T-cell response when CD80 interacts with CTLA-4.

Interaction of CD4 T cells with MHC-peptide complex and CD28

Induces the CD4 T cells to enter the cell cycle, proliferate, and differentiate into memory cells or effector cells.

Signal 1 and 2 in T-cell differentiation

Triggers entry of the T cell into the G1 phase of the cell cycle and induces cytokine Interleukin-2 (IL-2) expression.

Effector CD4 T cells

Promote activation of various immune cells with cytokine release, are short-lived, and carry out specialized functions.

Memory T cells

Are antigen-specific T cells that remain long-term after an infection has been eliminated.

TH1 subset

Secrete specific proinflammatory cytokines that cause up-regulation of immune response; includes IL-2, IFN-γ, and TNF-α.

TH2 subset

Secrete specific anti-inflammatory cytokines that downregulate the immune response; includes IL-4, IL-5, IL-6, and IL-10.

CD8 T cells

Require two signals for activation: Signal 1 from antigen-specific TCR and Signal 2 from antigen-independent co-stimulatory receptor-ligand interaction.

Interaction of CD8 T cells with MHC-peptide complex and CD28

Induces CD8 T cells to enter the cell cycle, proliferate, and differentiate into memory cells or effector cells.

Primary events in CD8 activation

Include conjugate formation, membrane attack, CD8 dissociation, and target cell destruction.

Conjugate formation

CD8 T cells and antigen interact and undergo this formation which is initiated with the help of Lymphocyte function-associated antigen 1( LFA-1)

Perforins

Polymerize and insert into the target-cell membrane to form cylindrical pores.

Granzymes (granzyme B)

Enters the cytoplasm of the target cell initiating the fragmentation of the target-cell DNA via apoptosis.

Apoptosis of Effector CD8 and CD4 T cells

Regulates their population in the circulation and downregulates their effector function effectively.