면역학 기초

* innate immunity
- epithelial cells
- sentinel cells in tissues [phagocytes (neutrophils, monocytes/macrophages), dendritic cells, mast cells, etc.]
- innate lymphoid cells (ILCs) (NK cells, etc.)
- plasma proteins (complements, etc.)

* ILCs
- Th1
- Th2
- Th17

* Lymphocytes

1. B lymphocytes: produces antibodies "humoral immunity"

: mature in the BM

1. T lymphocytes: "cell-mediated immunity"

: mature in the thymus
- CD4+ T cells

• helper T cells: help (1) B cells to produces antibodies, and help (2) phagocytes to destroy ingested microbes
• regulatory T cells (some): prevent/limit the immune response

- CD8+ T cells (=cytotoxic T lymphocytes, CTLs): kill cells harboring intracellular microbes

* interferon: a subgroup of cytokines (원래 viral infection에 방해하는 것으로 알려져 있었으나, 중요한 immunomodulatory function을 가진다)
- type I (interferon-alpha and -beta): the main function is to prevent viral replication
- type II (=interferon-gamma): macrophages 및 other cell types들을 activates

* interferon-gamma

* MHC
- class I: expressed on all nucleated cells
- class II: expressed mainly on APCs (dendritic cells, macrophages, and B lymphocytes)

* NK cells
- activating receptor
- [inhibitory receptor] - [(self) peptide antigen] - [MHC I] [normal cells]: NK cell의 inhibitory receptor는 (all healthy nucleated cels에서 발현되는) MHC class I molecule에 specific해서, healthy cells이 NK cells에 의해 파괴되는 것을 방지한다.

* [APCs] [MHC II] - [peptide antigen] - [TCR] [T-cell] -> T-cell mediated immune response (CMI)
- dendritic cells - MHC II (constitutive): principal inducers
- macrophages - MHC II (low or negative)
- B lymphocytes - MHC II (constitutive)