DEVELOPMENT OF LYMPHOCYTE POPULATIONS Flashcards
what is clonal selection and expansion
process by which some lymphocytes are destroyed and others are allowed to mature.
Lymphocytes bearing receptors for self are lost through the process
of clonal deletion before they become fully mature.
When a mature naïve lymphocytes binds to its particular antigen,
the lymphocytes proliferates and differentiates to form a clone
of cells all specific for that particular antigen.
What happens to lymphocytes bearing receptors for self during clonal selection?
Lymphocytes bearing receptors for self are lost through clonal deletion before they become fully mature.
What happens when a mature naïve lymphocyte binds to its specific antigen?
The lymphocyte proliferates and differentiates to form a clone of cells specific for that particular antigen.
What does clonal selection theory state about lymphocytes?
It states that an individual lymphocyte expresses receptors specific for a distinct antigen before exposure to it.
How does a lymphocyte respond when its antigen binds to its specific receptor?
The lymphocyte is activated, causing it to proliferate and form a clone of cells with the same immunologic specificity.
What are the two types of cells produced in clonal selection?
Memory cells (longer lifespan) and effector cells.
What is the function of memory cells in clonal selection?
Memory cells have a longer lifespan and are mobilized for future immune responses.
What is the role of MHC in antigen presentation?
MHC binds small peptides and presents them on the cell surface, allowing antigen recognition by T cell receptors.
What does the MHC help immune cells distinguish?
It helps immune cells distinguish “self” from “nonself.”
What types of peptides do MHC molecules display?
MHC molecules display both ‘self’ peptides (derived from the host’s own proteins) and foreign peptides (derived from pathogens).
What are Antigen Presenting Cells (APCs)?
APCs are cells that display antigen complexed with MHC on their surface.
What types of T cells are responsive to MHC I and MHC II?
MHC I is recognized by TC (cytotoxic T) cells, and MHC II is recognized by TH (helper T) cells.
What are the types of APCs/target cells for MHC I and MHC II?
MHC I targets all nucleated cells, while MHC II targets B cells, macrophages, and dendritic cells.
Where are protein antigens for MHC I and MHC II sourced?
MHC I presents endogenous (synthesized in the cell) protein antigens, and MHC II presents exogenous (internalized from the extracellular environment) protein antigens.
Where is the peptide loading site for MHC I and MHC II?
MHC I peptide loading occurs in the rough endoplasmic reticulum, and MHC II peptide loading occurs in the lysosome.
explain antigen processing and presenting of an exogenous antigens in phases of cell-mediated immunity.
- uptake of extracellular proteins into vesicular compartments of APC
- processing of internalised proteins in endosomal or lysosomal vesicles
- biosynthesis and transport of class II MHC molecules to endosomes
- association of processed peptides with class II MHC molecules in vesicles.
- expression of peptide-MHC complexes on cell surface
explain antigen processing and presenting of an endogenous antigens in phases of cell-mediated immunity
- production of proteins in cytosol
- proteolytic degradation of proteins
- transport of peptides from cytosol to ER
- assembly of peptide-calss I complexes in ER
- surface expression of peptide-class I complexes
