University:
York University
Course:
SC/BIOL 3120 | Immunobiology
Academic year:

2023
Views:

175

Pages:

3
Author:

Niklas

The Basics Activation of Adaptive Immunity Dendritic cells present at the site of infection/injury PAMP binds to the dendritic cell's PRR Signals cause phagocytosis of the antigen While phagocytosis occurs, the dendritic cell migrates to the secondary lymphoid organ, preparing to present the antigen Dendritic cells wait to present the antigen to their conjugate helper T-cells via MHC class II Antigen Presentation (overview) PAMP ligation induces DC maturation, which shapes MHC molecules on the surface Facilitates antigen presentation by inducing expression of APC costimulatory molecules MHC Proteins MHC: major histocompatibility complex Originally discovered when studying organ transplants 2 major types of proteins: MHC class I presents to CD8+ (cytotoxic T-cells) Found on ALL nucleated cells - everything except RBCs (which have no nucleus) Composed of an α-chain (α1, α2, α3) and β2-microglobulin (β2m) MHC Class I and II Both class I and class II contain a peptide-binding groove/cleft where small peptides bind An MHC class I is also an MHC class II The MHC Locus and Inheritance Alleles: alternative versions of a gene Single nucleotide polymorphisms (SNPs): a polymorphism that comes from a single nucleotide Co-dominant: genes from maternal and paternal chromosomes are both expressed Haplotype: a set of alleles on linked genes that are usually inherited together Outbred populations tend to have more diverse MHC regions Inbred populations tend to be more homozygous Isogenic: genetically identical Pangenic: identical at every locus except one Polygenic: the protein is the product of more than one gene Polymorphic: there are multiple versions of the proteins MHC Genes In humans, MHC is also known as HLA (human leukocyte antigen complex) MHC class I presents to CD8+ (cytotoxic T-cells) MHC class II presents to CD4+ (helper T-cells) TNF: tumor necrosis factor HLA-DP, HLA-DQ, HLA-DR: genes within each class (I and II) MHC Class I and II The MHC is polymorphic and polygenic, leading to different combinations. MHC genes are co-dominant. MHC can express many molecules at once. Haplotype Inheritance Every possibility of combination can be expressed with the progeny from two parents. Recombination typically does not occur in the MHC. MHC Diversity Biologically, diversity is very important. The likelihood of having the exact same alleles on a cell is very low. Genetic similarity can be assessed through blood typing or HLA typing. Reduced genetic similarity can lead to reduced immune response.