Home / Summaries / Class notes - Immunobiology / cells-antigens-dcs

Cell-mediated Imunnity

6 important questions on Cell-mediated Imunnity

How do T cells get activated by dendritic cells?

DCs carry antigens from sites of infection to secondary lymphoid tissues. DCs maturate by this transport and processing the antigens to peptides. The peptides of the antigen have a higher affinity for the MHC molecule than the self-peptide bound to it. The T cells are activated once they find out the MHC-antigen complex has a foreign molecule bound to it, activatin the cell.

What various pathways can be used by DCs to process and present degraded antigen proteins?

1. Receptor-mediated endocytosis of bacteria (CD4 T cell) --> via vesicle/endosome
2. Macropinocytosis of bacteria or viruses (CD4 T cell) --> via vesicle/endosome
3. Viral infection (CD8 T cell) --> via ER
4. Cross-presentation of exogenous viral antigens (CD8 T cell) --> via ER

How do naive T cells home to the secondary lymphoid tissues?

determined by chemokines and cell adhesion molecules --> T cells have receptors that bind to the proteins on the surface of lymph node epithelial cells, so they can enter the lymph node

After naiev T cell activation effector T cells are formed by the cytokine enviroment. What type of T-helper cells are there?

- TH1: activates macrophages to become highly microbicidal: intravesicular bacteria are killed by the activated macrophage
- TH2: activate cellular and antibody response to parasites
- TH17: enhance neutrophil response
- TFH: activate B cells to refine the antibody response --> Tfh and naïve B cell that they help, recognize different epitopes of the same antigen
- Treg: suppress other effector T cells --> suppression of autoreactive T cells by Treg needs both T cells to engage the same antigen-presenting cell

What would be the expected phenotype of people who have no functional AIRE?

Autoimmune diseases of only those organs that contain tissue-specific antigens

Why is there a big difference in thymocyte numbers observed when comparing TCRα-/- to TCRβ-/- thymocytes?

When pre-T cell receptors have formed (with a successful TCRbeta) the cell divides several times so there is a 100 fold increase. This happens before the TCRalfa development and after the TCRbeta.