27 Questions
What is the function of autophagosomes?
Contain cytoplasmic content and fuse with lysosomes
Under what conditions do autophagosomes form?
In the presence of a pathogen
What is the main mechanism of rejection of transplanted organs?
Allorecognition
What is the difference between direct and indirect allorecognition?
Direct targets donor MHC molecules, while indirect targets recipient APCs
Which genes encode the alpha and beta chain of MHC Class II molecules?
HLA-DQ
What does polymorphism refer to in terms of MHC genes?
Multiple variations or alleles existing for each gene
Where are HLA genes located in humans?
Chromosome 6
Which T cell recognition involves targeting regardless of the peptide presented?
Direct allorecognition
What percentage of all T cells in an organism can react to non-self MHC molecules?
1-10%
What characteristic does a locus represent?
Chromosomal location of a gene
How many HLA-A alleles are there in the range of HLA-A1 to HLA-A2041?
2000 alleles
What term describes the particular combination of MHC alleles found on a single chromosome?
Haplotype
How many different MHC-I alleles can be expressed in an individual, considering inheritance from both parents?
6 alleles
What feature of MHC genes makes human transplantation difficult?
Heterozygosity at each locus
Where do most differences in MHC expression exist within the molecule?
Peptide Binding Groove
Which term describes having multiple genes that encode for proteins with the same function?
Polygeny
What process involves cytosolic peptides being presented on MHC Class II through autophagy?
Cross-Presentation
What is the unique ability of dendritic cells in the immune system?
Cross-presenting antigens
How are dendritic cells 'licensed' to perform cross-presentation of antigens?
By activating CD4+ T cells
What is the role of a CD4+ T cell in the process of cross-presentation by dendritic cells?
Granting permission to dendritic cells for cross-presentation
What is the significance of the 'license' granted by CD4+ T cells to dendritic cells?
It enables the redirection of exogenous antigens to MHC class I molecules
Which type of T cell needs to be activated first for dendritic cells to license and cross-present antigens?
CD4+ T cell
What happens after dendritic cells get permission from CD4+ T cells to redirect exogenous antigens?
They activate CD8+ T cells.
Why is the redirection of exogenous antigens onto MHC class I molecules important?
To prime CD8+ cytotoxic T-cell responses
What is the mechanism by which dendritic cells redirect exogenous antigens onto endogenous pathways?
By receiving permission signals from CD4+ T cells
In the context of immune response, what is the role of cross-presentation by dendritic cells?
To activate cytotoxic immune responses against pathogens
How does cross-presentation by dendritic cells contribute to immune surveillance?
By detecting and eliminating infected or abnormal cells
Explore exceptions to the rules of antigen presentation in immunology, such as cross-presentation, presentation of cytosolic peptides by MHC class II molecules, and allorecognition. Learn how exogenous peptides can be presented on MHC class I and vice versa through cross-presentation by dendritic cells.
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