Exam 2 -Adaptive Immunity Flashcards
epitope
part of antigen which is recongnized by BCR, TCR, or Abs, can be multiple on one antigen
Makes a good antigen
large (more epitopes)
Comple/Heterogenecity (vs. repeating subunits)
Proteins (elicit strong response) vs polymers/lipids = weak
response generated by polymers
weak
lipid antigen response
none, they are haptens (need complex)
Problem with encapsulated bacteria
covered in polysachharrides, immune system is not easily induced
Bacterial response vs fungal
fungal is stronger b/c they have many antigens whereas bacteria have just one with many epitopes
site of lymphocytic origin and maturation
primary lymphoid tissue
produces T cells
Thymus
Produces B cells
Bone marrow
Secondary lymphoid tissue
sites where lymphocytes encounter antigen (lymph, spleen, clusters of lymphoid tissue (MALT-tonsils) and GALT (gut)
ALT
associated lymphoid tissue
Development of Lymphocytes
Stem cell in bone marrow –> B or T progenitor cell –> matures in bone or thymus respectively, mature cells enter blood –> secondary lymph tissue to look for antigen –> enter back into circulation if they do not find antigen
Naive lymphocytes
have antigen receptors, but have not yet encountered their antigen
Activated Lymphocytes
have found and bound their antigen to their receptor, and have recieved a co-stimulatory signal (allowing them to expand and differentiate into effector and memory cells)
Effector lymphocytes
short-lived descendants of activated lymphocytes,armed with the ability to carry a out a specific immune function such as secreting antibodies, cytokines, or killing infected cells
Memory Lymphocytes
long-lived descendant of activated lymhocytes; can quickly become effector cells upon second exposure-they remain in the body after infection is cleared so next time the response is rapid –> effector cells
T Cell development and Education
In the thymus, progenitor cell matures into a naive T cell and expresses TCR which is specific for ONE antigen (recombinatin), T cells then mature in the thymus as self anitgens are selected against (+ are weak and kept and - are strong and destroyed apoptosis); lastly the T cells express a glycoprotein (CD4 or CD8)
Genes for specific TCR
specific to one epitope so made with genetic recombination and deletion of autoimmune clones; T cell then to get activated they are processed or presented and gets a costim signal; once activated they prolif
+ T cells
allowed to stay; only weakly bind self antigens
- T cells
killed via apoptosis b/c they strongly bind self antigens
T cells Express what once mature
a glycoprotein, either CD4 or CD8
Needs to happen for T cells to be activated
Antigens to T cells processed and presented; and costimulatory signal required
Most T cells become
effector cells
CD8+ cells mostly become
cytotoxic T cells
CD4+ cells mostly become
Helper T cells (TH1 or TH2)
Cells which do not become effector T cells
Memory CD4+ and memory CD8+ cells
Negative Selection of B cells
B cells that react strongly to self antigen (autuimmune clones) are deleted in bone marrow via apoptosis
B cell receptor
expresses IgM (immunoglobin protein) on surface as receptor; has two antigen binding sites (for the same antigen-NOT different) and binds free soluble antigens such as protein, polysach, or lipids
T Cell Receptor
A single antigen binding site; binds PROCESSED antigens (cut up into pieces) that are presented TO THEM by MHC receptor (NOT soluble antigen);
These antigens are mostly proteins and internal linear peptides produced during processing of antigen and bound by MHC
T cell receptors have ____ binding sites
one binding site for antigen
B Cell Receptors have _____ binding sites
two antigen binding sites for the same antigen; expressed as IgG
B Cell receptors bind
Free soluble protein, lipid, or polysachs
T cell receptors bind
Processed protein which is presented to them by MHC-commonly internal linear peptides
Number of eptiopes recognized by a one BCR or TCR
one!
Number of receptors on a single T/B cell
50,000 BCRs/TCRs
Population of T and B cell responds to _____ epitopes
100 million; but NOT 100million receptor genes
How do B and T cells detect so many epitopes?
gene rearrangement of cassetes; segements of genes are randomly cut and sliced during development and via genetic recombination form a functional receptor gene; thus autoimmune cells must be removed (maturation)
Major Phases of T and B cells
Selection and activation of naive lymphocytes, and expansion/proliferation and differentiation into effector cells
Selection
upon entry into immune system each antigen or processed antigen is recognized by a genetically distinct lympocyte with the correct receptor
Activation
signals from another cell type are needed to go further
Expansion
upon activation, the lymphocyte proliferates and differentiates into a larger population of identical cells which can react to the same exact type of antigen!
Helper T cell Role
secrete cytokines that activate other cells in the immune system
Helper cells come from
Naive CD4 T cells
TH1 secretes
IL-2 and IFN gamma to activate CD8+ cells
