Antigen Processing and Presentation Quiz

Questions and Answers

What are Major Histocompatibility Complex (MHC) molecules primarily responsible for?

Transporting nutrients across the cell membrane

Binding processed antigen peptides for T lymphocyte recognition (correct)

Binding to circulating antibodies

Degrading endogenous proteins

Which class of MHC molecules is primarily found on professional antigen presenting cells?

MHC Class II (correct)

MHC Class IV

MHC Class I

MHC Class III

What type of T cell interacts with MHC Class I molecules?

Regulatory T cells

CD4+ helper T cells

Memory T cells

CD8+ cytotoxic T cells (correct)

Which of the following statements about MHC Class I and II is correct?

MHC Class II is primarily found on antigen presenting cells. Signup and view all the answers

What is true regarding the genetic characteristics of human leukocyte antigens (HLA)?

They are polygenic with several loci encoding similar functions. Signup and view all the answers

What is the primary function of MHC class I molecules?

To present antigens to T cells Signup and view all the answers

Which cells are classified as professional antigen presenting cells?

Dendritic cells Signup and view all the answers

How do T cells recognize antigens?

Through MHC molecules presenting peptide fragments Signup and view all the answers

What distinguishes MHC class II molecules from MHC class I molecules?

Class II is primarily found on professional antigen presenting cells Signup and view all the answers

What is the role of the T helper cell in the immune response?

To regulate the activation of B cells and other T cells Signup and view all the answers

Study Notes

Antigen Processing and Presentation

Antigen processing involves capturing and degrading antigens for presentation to T cells via Major Histocompatibility Complex (MHC) molecules.
T cells require peptide-MHC complexes for recognition, while B cells can bind free antigens directly.
MHC molecules, encoded by multiple loci, present processed antigen fragments to T cells, pivotal for initiating an immune response.
MHC class I (HLA class I) is present on all nucleated cells, presenting endogenous peptides to CD8+ T cells.
MHC class II (HLA class II) is mainly found on professional Antigen Presenting Cells (APCs) like dendritic cells, macrophages, and B cells, presenting exogenous peptides to CD4+ T cells.

Structure and Function of MHC

MHC class I consists of four domains (α1, α2, α3, and β2-microglobulin) and interacts with CD8+ T cells.
MHC class II consists of four domains (α1, α2, β1, and β2) and is recognized by CD4+ T cells.
Human MHC is referred to as Human Leukocyte Antigen (HLA) with two classes: HLA class I and HLA class II, each being polygenic and polymorphic.

Antigen Sources and Presentation Mechanisms

Endogenous antigens (e.g., viruses, tumors) are modified and presented via MHC class I; they undergo degradation in the cytosol by proteasomes.
Exogenous antigens (e.g., bacteria) are taken up through endocytosis or phagocytosis, processed in lysosomes, and presented via MHC class II.
For MHC class I loading, peptides are transported to the endoplasmic reticulum (ER) and bind to MHC class I molecules before transport to the cell surface.
MHC class II molecules are synthesized in the ER with an invariant chain blocking the peptide groove, replaced by antigen peptides after the chain is cleaved.

MHC Restriction and Immune Response

T cell recognition is dependent on peptide-MHC complexes; T cell receptors (TCRs) recognize these complexes rather than solitary peptides.
MHC restriction ensures T cells only respond to self-MHC-displayed peptides, crucial for distinguishing self from non-self.

Clinical Relevance

MHC compatibility is crucial in organ transplantation; mismatches can lead to rejection.
Certain MHC genotypes increase the risk of autoimmune diseases such as Type 1 diabetes and rheumatoid arthritis.
MHC diversity impacts susceptibility to infections and can affect disease outcomes in infections like HIV and malaria.
Understanding MHC's role in presenting tumor antigens can improve effectiveness in cancer immunotherapy and personalized medicine approaches.

Description

Test your knowledge on the structures and functions of MHC class I and II proteins. This quiz covers their role in the immune response, as well as the types of antigens processed by these molecules. Additionally, you'll explore professional antigen presenting cells and the function of T helper cells.