Clonal selectional theory Flashcards
What are the major features of clonal selection?
1.The immune system is comprised of a heterogeneous population of
billions of different lymphocytes.
- Each individual lymphocyte is specific for a single epitope of an antigen.
- This antigen-specificity is by virtue of each lymphocyte’s unique surface
receptor. - Only a small number of lymphocytes will recognize a specific antigen.
- Recognition of an antigen (i.e. interaction of the antigen with the
lymphocyte receptor) signals the cell to undergo proliferation. This
results in a clone of cells all expressing receptors with the same antigen-
specificity. - Proliferating lymphocytes will eventually differentiate into either effector
cells or memory cells. - Self-reactive lymphocytes are deleted at an early stage in lymphoid cell
development.
the antigen-specific receptors in the case of B cells are membrane-bound _______
Immunoglobulins
What reaction would the B and C cells have if there is an antigen exposure subsequent to the initial exposure?
-memory
cells are more easily “triggered” than so-called naïve lymphocytes.
-this means that the immune system is able to respond in a shorter
period of time upon subsequent infection.
-Memory cells also produce an immune response larger in magnitude than naïve lymphocytes.
What are antibodies? (Ab or Ig)
glycoproteins found in SERUM, extracellular fluid, and mucosal secretions.
-SECRETED by EFFECTOR B cells in response to foreign substances called antigens (Ag)
Antibodies are antigenic _____
specific
-they only bind to ONE SPECIFIC ANTIGEN
What major fractions can be obtained when separating serum? and which one can you find immunoglobulin?
albumin, alpha-globulin, beta-globulin, and y-
globulin
y-globulin
What chains do antibody molecule MONOMER consist of? and what is their confirmation?
TWO heavy H chains
TWO light L chains
**Each H chain is linked COVALENTLY to an L CHAIN by a disulfide bond formed between cystine residues
** The two H chains are also linked to each other by s-s bonds, producing a flexible region that is referred to as a HINGE REGION
EVERYTHING FORMS Y SHAPE
what is a hinge region?
the flexible region produced by The two H chains linked to each other by s-s bonds
How can an antibody monomer be split to become functional units? and what are each of the functional units functions?
the antibody molecules are cleaved into various parts by using PAPAIN (enzyme)
Fab- include one light chain and part of a heavy chain. contains ONE BINDING site for an antigen. (TWO fabs per monomer—- two binding sites for an antigen)
*EACH FAB DINIGN SITE IS IDENTICAL!! bind to the same antigen
Fc- made up of two parts s of heavy chains. Determines SPECIFIC EFFECTOR FUNCTIONS that the immune system will take on the antigen-antibody complex
What is a domain?
tightly folded regions of about 100 amino acids on each Immunoglobulin chain of a monomer
light chain has 2 domains
heavy chain has 4 domains
What are the variable regions (Vh and Vl) and the constant regions (Ch and Cl) in an immunoglobulin?
Variable regions- domains at N-terminus in both heavy and light chains, where ANTIGEN- SPECIFICITY of a particular antibody resides.
Vh and Vl combine together to FORM a SHAPE that recognizes and BINDS antigens together (antigen binding site)
What are hypervariable regions? (or CDRS)
-three segments of extreme high variability in both Variable regions for H and l chains. (Three hyper variable regions in EACH DOMAIN)
-when the Vh and Vl variable regions bind (uniting a total of six variable regions or 6 CDRS), they create a binding site for a specific epitope.
**HYPERVARIABLE regions for Vh DIFFER from the hypervariable regions of VL
what are the five CLASSES of immunoglobulin (Isotypes) in mammals, their H CHAIN DESIGNATION, and their number of CDRS on each variable region?
Which class of immunoglobulin is the most prominant?
IgG
Where are the hinges present on each type of immunoglobulin?
IgG, IgA, IgD - between Ch1 and cH2 (HAVE 3 CDR’S)
IgM, IgE- between ch2-ch3 ( HAVE 4 CDR’S)
*** the constant region of each class is THE SAME to the others OF THEIR CLASS
Which Ig’s are classified as polymeric Ig’s and why?
IgM and IgA
IgM is found in the SERUM (circulation only– not tissue due to size) as a PENTAMER.
it is held together by a J CHAIN
has 10 binding sites (due to 2 binding sites per monomer attached)
IgA found in serum as monomers and dimers.
-ONLY found as DIMERS in SECRETIONS (secretory IgA)
-regular DIMERS have a J CHAIN only
-Secretory IgA have J chain and a SECRETORY COMPONENT
what is multiple myeloma? and how can it be found?
-cancer of a SINGLE plasma cell (effector B cells)
-caused by a single plasma cell becoming neoplastic (growing out of control) and crowding the bone marrow
-produce large amounts of myeloma protein
-found by VERY large y-globulin peak in serum
-IgG spike goes up and and calcium levels go up
What are the types of light chain isotypes?
what Ig isotope classes do camelids have?
**Only have two IgG sublclasses
-Have Vh region (called VHH) that forms binding site WITHOUT A LIGHT CHAIN
