Adaptive Immunity 1 Flashcards
(42 cards)
Describe adaptive immunity.
Induced from antigen encounter
Use gene rearrangements to to create different antigen receptors
Memory, specific, self-tolerance
Two branches cell mediated (T and B cells) and humoral (antibody-mediated)
Define antigen
Any foreign particle that enters the body such as dust, food and any microorganisms
Define immunogen
Substance that induces a specific immune response
All immunogens are antigens but not all antigens are immunogens
Define haptens
Small molecules that don’t invoke an immune response on their own but can when coupled to a carrier molecule
Define epitope or antigenic determinant
Portion of an antigen that combines with the products of a specific immune response
Define Antibody
Specific protein produced in response to an immunogen and that reacts with an antigen
when are receptors for the adaptive immune system generated?
During lymphocyte differentiation
Compare B and T cells.
B cells: humoral
Attack invaders outside the cell (intact)
Transmembrane receptor: 2 heavy 2 light chains
T cells: cell-mediated
Transmembrane receptor: 2 non-identical proteins
Attacks invaders inside the cells
Compare the effector B cells vs effector T cells.
Effector B cells- plasma cells secrete antibodies, secreted form of B cell receptor
Effect T cells- CD4 helper, CD 8 cytotoxic
Where do B and T cells mature, where do they circulate, how do they become effector cells? Which of the two undergo affinity maturation?
B (bone marrow), T (thymus): central lymphoid organs
Circulate in blood and peripheral
Effector when they encounter specific antigens that bind to BCR and TCR
When antigen binds:
Cells migrate to lymph nodes and peripheral
Proliferate
Differentiate into effector
B cells undergo affinity maturation to become better fit
Define clonal selection
Naive B lymphocytes rearrange DNA in bone marrow resulting in antibodies with unique antigen binding sites
Clonal selection is when an antigen encounters the immune system, at least 1 b cell receptor will react with it
Describe clonal expansion and contraction.
Proliferation of lymphocytes after antigen activation
After the antigen is gone, activation ends, contraction of effectors, memory cells remain in bone marrow
Describe clonal deletion and tolerance.
During B cells development, deletion of lymphocytes that react with self in primary immune organs (central tolerance)
Deletion of self reactive in peripheral lymphoid organs (peripheral tolerance)
Occurs through apoptosis
What are the receptors on the surface of B cells? What helps to antibody to bind an antigen?
Antibodies
Helper T cell
Describe the process of immunoglobulin gene assembly. What proteins carry out this process?
Requires DNA recombination and deletion
Each cell has 2 copies of Ig gene, only 1 rearranges and expressed by allergic expression
Requires recognition of recombination signal sequences
RAG-1 and RAG-2 carry out recombination
How do we get antibody diversity? Is B cell differentiation antigen independent or dependent?
Many combinations in recombination
Junctional diversity- intro of non-templates nucleotides
Antigen independent rearrangements before encounter
Antigen dependent- affinity maturation
Describe B cell activation.
Antigens are recognized by immature B cells
B cells phag and degrade antigens in to peptides in lysosomes
Peptide fragments are carried to B cell surface through MHC 2 and recognized by helper T cells
Helper T cells secrete cytokines that induce B cells to become plasma cells, affinity mature, produce specific antibodies (class switching)
Describe when immunoglobulin class switching occurs.
Different classes results from genetic recombination
Induced by cytokines from T cell
mRNA splicing is the last step
What are the 5 types of immunoglobulin classes (isotypes) in human serum? What are their shapes? What are they named after?
IgM (pentamer, largest)
IgG (Y monomer, most common)
IgD (Y monomer)
IgE (Y monomer)
IgA (Y dimer connect by J chain)
Named based on constant heavy chain
Describe IgM
First responder
Pentamer
Classical complement pathway
Found on B-lymphocytes as B-cell receptors
Describe IgG
Crosses placenta
Most abundant
Fc region
Activates complement via classical pathway
Binds to both macrophages and neutrophils to enhance phagocytosis
Induce ADCC (Killing of an antibody‐coated target cell through a non-phagocytic process, characterized by the release of cytotoxic granules or by the expression of cell death‐inducing molecules)
Describe IgA
Made in mucosal associates lymphoid tissue
Body secretions (breast milk)
Blocks attachment of bacteria and viruses to mucous
Dimer
Protested from digestive enzymes
Fc binds to mucous and helps it trap microbes
Do we have memory cells on our mucousal membranes?
Yes tissue resident memory cells from IgA
Describe Ig D
Monomer
Found on surface of Blymphocytes as B cells receptor
Role in elimination self reactive auto antibodies
