mhc extra reading

Question 1

b cell and t cell binding ranges?

Answer 1

Most T lymphocytes recognize only short peptides, whereas B cells can recognize peptides, intact folded proteins, nucleic acids, carbohydrates, lipids, and small chemicals. As a result, T cell–mediated immune responses are usually induced by foreign protein antigens (the natural source of foreign peptides), whereas humoral immune responses are induced by protein and nonprotein antigens. Some T cells are specific for small chemical substances such as urushiol of poison ivy, β-lactams of penicillin antibiotics, and even metal ions such as nickel and beryllium. In these situations, it is likely that the chemicals bind to self proteins, including MHC molecules, and that T cells recognize the modified self peptides or altered MHC molecules (rather than the chemicals themselves)

Question 2

what does mhc polymorphism impact?

Answer 2

MHC molecules are highly polymorphic, and variations in MHC molecules among individuals influence both peptide binding and T cell recognition.

Question 3

mhc restriction?

Answer 3

A single T cell can recognize a specific peptide displayed by only one of the large number of different MHC molecules that exist. This phenomenon is called MHC restriction

Question 4

factors impacting mhc class 2 expression?

Answer 4

Dendritic cells- Constitutive; increases with maturation; increased by IFN-γ and T cells (CD40L-CD40 interactions)
Principal Function: Antigen presentation to naive T cells in initiation of T cell responses to protein antigens (priming)

macrophages- Low or negative; increased by IFN-γ and T cells (CD40L-CD40 interactions).
principle function: Antigen presentation to effector CD4 + T cells in effector phase of cell-mediated immune responses (T cell–enhanced killing of phagocytosed microbes)

B lymphocytes- Constitutive; increased by IL-4, antigen receptor cross-linking, and T cells (CD40L-CD40 interactions)
principle function: Antigen presentation to CD4 + helper T cells in humoral immune responses (helper T cell–B cell interactions)

Vascular endothelial cells Inducible by IFN-γ (also in various epithelial and mesenchymal cells); constitutive in some human blood vessels
principle functions: May promote activation of antigen-specific T cells at site of antigen exposure and in organ grafts

Thymic epithelial cells- constitutive expression.
role:Positive and negative selection of developing CD4 + T cells

Question 5

APC role?

Answer 5

APCs also secrete cytokines that play critical roles in the differentiation of naive T cells into effector cells.
The cytokines that drive the development of CD4 + T cell subsets are produced by APCs (primarily dendritic cells [DCs] and macrophages) and other immune cells (such as NK cells and mast cells) present in the lymphoid organ where the immune response is initiated.
DCs that encounter microbes and display microbial antigens are activated to produce cytokines (as well as costimulators) as part of innate immune responses to the microbes (see Chapter 4 ). Different microbes may stimulate DCs to produce distinct sets of cytokines.