Immunology and Infection Lecture Flashcards

Flashcards based on the Immunology and Infection lecture notes covering Major Histocompatibility Complex (MHC) and Transplantation Biology.

Where are the MHC genes located in humans?

Chromosome 6, referred to as the HLA complex.

What is the role of MHC complexes?

To trigger a T-cell response when presenting non-self peptides.

Which T-cells interact with MHC Class II?

T helper cells (CD4+).

Which T-cells interact with MHC Class I?

Cytotoxic T- cells (CD8+).

What are three key characteristics of MHC genetic organization?

Highly polymorphic, high linkage, and co-dominant expression.

What is the consequence of MHC allele diversity in a species?

Wide inter-individual variation in the peptide specificity of the MHC.

What is the function of MHC polymorphism?

Mediates protection of the species from all pathogens.

Which cells express MHC Class I?

All somatic cells.

What type of peptides do MHC Class I molecules bind?

Endogenous peptides.

Which cells express MHC Class II?

Antigen Presenting Cells (APCs) only.

What type of peptides do MHC Class II molecules bind?

Exogenous peptides.

What proteins are associated with the MHC Class III region?

Complement proteins.

What is the result of the high linkage of MHC genes?

Low recombination frequency.

What is the molecular weight of the alpha chain of MHC Class I?

45 kDa.

What is the molecular weight of the beta-2 microglobulin protein?

12 kDa.

What domains of the alpha chain form the peptide-binding groove in MHC Class I?

α1 and α2 domains.

What superfamily does MHC Class I belong to?

Ig superfamily.

How many external alpha domains does the alpha chain of MHC Class I possess?

Three.

What is the approximate length (in amino acids) of the transmembrane domain of the MHC Class I alpha chain?

25 amino acids.

What is the approximate length (in amino acids) of the cytoplasmic anchor of the MHC Class I alpha chain?

30 amino acids.

What is the size range of the peptide fragment that binds to the cleft formed by the alpha1 and alpha2 domains of MHC Class I?

8-10 amino acids.

Is Beta-2 microglobulin covalently or non-covalently associated with the MHC I alpha chain?

Noncovalently.

What type of molecule is the MHC Class II molecule?

Heterodimer.

What are the approximate molecular weights of the alpha and beta chains in MHC Class II?

33 kDa for alpha and 28 kDa for beta.

What domain pairings form the peptide-binding cleft in MHC Class II?

α1 and β1 domains.

What is the range in size of peptides accommodated by the MHC Class II cleft?

13-18 amino acids.

To which T cells do the peptides presented by MHC Class I proteins go to?

CD8+ T cells.

From what are the peptides presented by MHC Class I proteins derived?

Intracellular proteins.

What is the typical length of the peptides presented by MHC Class I proteins?

8–10 amino acids, most commonly 9 amino acids.

What type of residues anchor a peptide into the MHC Class I groove?

Anchor residues.

What is the role of APCs?

Present antigen on MHC.

What cells are considered APCs?

Dendritic cells, macrophages, and B cells.

What is the length of the peptide that binds to MHC Class II?

12-20 amino acids long.

What is the length of the peptide that binds to MHC Class I?

8-9 amino acids long.

Where does exogenous antigen processing derive antigen from?

Phagocytosis or internalization of antibody/antigen complex.

What is the process for the endogenous antigen processing of proteins?

Proteins within a self cell are processed via the proteasome, transported by TAP, and presented by MHC class 1.