Chapter 5 Flashcards
(28 cards)
What is CD4 on?
helper T cells
What is CD8 on?
Cytotoxic T cells
What does T lymphocyte activation by APCs lead to?
Cell multiplication (“cloning”) and Cell differentiation (memory cells, effector cells)
What is the overall difference between B cells and T lymphocytes (T cells)?
They both recognize and bind antigen through highly variable antigen-specific receptors. B cells’ sole function is to make antibodies, while T cells have diverse roles in adaptive immunity, all of which involve intimate interactions with other cells.
What is a T lymphocyte? (T cell)
a minority type of circulating T cell that expresses an antigen receptor composed of a gamma chain and a delta chain. These cells recognize different types of antigen from those recognized by alphabeta T cells, including phosphoantigens and are not dependent on the presentation of antigen by MHC class I and II molecules. gammadelta T cells are more abundant in the gut and other tissues than in the blood.
What is a MHC molecule?
(major histocompatibility complex molecule) large cluster of mainly immune-system genes present in all vertebrates that encodes, among other proteins, the highly polymorphic MHC class I and class II molecules, which present peptide antigens to T cells and are the basis of an individual’s tissue type
How many antigen-binding sites does a T cell receptor have?
only one
T cell receptors are always ___________ and they have no _______ form equivalent to an antibody.
membrane bound, secreted
There are no T-cell equivalents of the processes in B cells that _____
hypermutate the antigen binding site and switch the heavy chain isotype
How many polypeptide chains do T cell receptors have?
Two, TCR alpha and TCR beta
Why do immunoglobulins have two or more binding sites for an antigen?
It enables antibodies to form high-avidity multipoint attachments to the repetitive antigens present on microbial surfaces.
After stimulation, T cell receptors _______
remain unchanged
The T cell receptor alpha chain locus is on human chromosome ____, and the beta chain locus is on human chromosome ____
7,14
What happens in the thymus?
It is where T cells develop and where T cell receptor genes are rearranged
Like all proteins destined for the cell membrane, newly synthesized alpha and beta chains enter the __________
endoplasmic reticulum
What happens in people lacking functional CD3 delta or CD3 epsilon chains?
Transport of T cell receptors to the cell surface is inefficient, and their T cells have abnormally low numbers of receptors that do not signal effectively. As a consequence of both the low receptor numbers and impaired signal transduction, such individuals are immunodeficient.
Why must the Ag be processed for T cell receptors?
Epitopes are inaccessible in the intact protein
When stimulated, APCs produce/ express:
More MHC II, cytokines (IL-1, TNF)
What do MHC molecules do?
they are proteins found on the surface of ells that act as markers to present small fragments of proteins (peptides) to the immune system, allowing T cells to identify and respond to foreign invaders like viruses or bacteria by recognizing these presented peptides as “non-self”
MHC class I presents the antigens of ________
intracellular pathogens
MHC class II presents the antigens of ________
extracellular pathogens
Which type of effector T cell is related to MHC I?
The cytotoxic T cell which recognizes antigens presented by MHC class I molecules and defends against intracellular infection
Which type of effector T cell is related to MHC II?
The helper T cell, which recognizes antigens presented by MHC class II molecules and defends against extracellular infection
How are the cytotoxic and help T cells easily distinguished?
Cytotoxic T cells all express the CD8 cell-surface protein, whereas helper T cells all express the CD4 cell-surface protein
