Immune System Part 2 Flashcards
Specific (Adaptive) Immunity
Can recognize and remember specific pathogens
-Ability to mount stronger attacks each time the pathogen is encountered
Antigens
Foreign molecules (proteins or polysaccharides) from pathogens
- Stimulate immune system directly or
- Processed and presented to immune system by APCs
B Lymphocytes
Produce and release antibodies into plasma to act at a distance
- Mature in bone marrow
- Confer humoral immunity
- Antigen binding to a B cell receptor activates cloning
T Lymphocytes
Antibodies remain bound to cell to destroy pathogens upon contact
- Mature in thymus
- Cell-mediated defense: bacteria, viruses, parasites, fungi, abnormal cells
- Activated by antigen bound to MHC molecule
- Can’t respond to antigen directly
B Lymphocytes Memory Cells
Formed during primary immune response, needed for secondary immune response
- Long lived, inactive close
- Respond rapidly to subsequent attack
B Lymphocytes Plasma Cells
Produce and release antibodies
- initial immune response lifespan is 3-4 days
- Following affinity maturation lifespan is years, cells continue to secrete high levels of antibodies
CD4 Cells (T lymphocyte)
Activated by MHC class II
- Produce memory cells and helper cells
- Helper cells stimulate other immune cells (CD8, macrophages, B cells, nonspecific WBCs) by secreting cytokines
CD8 Cells (T lymphocyte)
Activated by MHC class I
- Produce memory and cytotoxic cells
- Cytotoxic cells kill abnormal cells
- Perforin creates holes in target cells
- Granzymes signal apoptosis
Suppressor (Regulatory) T cells
CD4+/CD25+/FoxP3+
- Inhibit excessive immune response
- Reduce inflammation
Natural Killer T cells (NK-T cells)
Recognize glycolipid antigen presented by CD1d
-Can perform functions of either helper or cytotoxic t cells
Positive Selection
Ensures immune response
- Cells that bind MHC/antigen complex w/ adequate affinity receive vital survival signal
- Cells w/ inadequate affinity die via apoptosis
Negative Selection
Prevents autoimmune response
-Cells that interact strongly w/ self-antigen receive apoptosis signal
Off Switch for T cells
After infection has been removed
-Producing and secreting FAS ligand, which binds back in an autocrine manner to the FAS receptor on T cells causing apoptosis
Lymphokine
Cytokine specific for subsets of lymphocytes
Interleukin 1 (IL-1)
Induces fever
Induce proliferation and activation of lymphocytes
Increase number of bone marrow cells
Cause degeneration of bone joints
IL-2
Produced by helper T cells
-Activate cytotoxic T cells especially during microbial infection
IL-4
Produced by helper T cells
- Activates B and T cell proliferation
- Differentiation of CD4 T cells into helper T cells (that can make more IL4)
- Induces B cell glass switching to IgE
- Up-regulates MHC class II production
IL-5
Produced by helper T cells and mast cells
- Stimulate cell growth
- Increase immunoglobin secretion, key mediator in eosinophil activation, associated w/ allergic diseases
IL-10
Produced by monocytes, lymphocytes, and mast cells
-Anti-inflammatory that counteracts inflammation in allergic reactions
IL-12
Produced by dendritic cells, macrophages, and Blymphoblastoid cells in response to antigenic stimulation
-Involved in differentiation of naive T cells into helper T cells
MHC Markers
Recognition of normal self tissues
- HLA
- Class 1 and Class 2
Class I MCH
On almost every cell in body except RBCs
Activation of cytotoxic T cells
Class II MCH
On B cells and APCs
- Presents antigens to lymphocytes
- Activation of Helper T cells
Antibody structure
2 heavy chains joined with disulfide bond and 2 light chains
-variable region at top and constant region below it
- Fab fragment
- Fab2 fragment
- Fc fragment
- variable region
- every but lowest constant portion
- constant portion of both chains
IgM
1st antibody produced -membrane bound -allow helper t recognition -Primary antibody against A and B antigens on RBCs -Large pentameter 5-15%
IgG
Target antigen tagged cell for destruction (“Goodbye cell”)
-Primarily in secondary immune response
-Equal in blood and tissue
-Can cross the placenta providing passive immunity
80%
IgA
In external secretions
-prevents pathogen entry across mucus membranes
10-15%
IgE
Allergic response
<1%
IgD
Signals B cell activation
<1%
Antibody Generation (VDJ)
VDJ recombination of variable region
- Segment of of DNA b/w D and J region gets removed and deleted
- Segment of DNA b/w V and DJ gets removed and deleted
Somatic Hypermutation (SHM)
- Antibody generation
- Programmed process of mutation in variable regions
- C becomes U
- Mutations repaired by DNA mismatch repair enzymes
- Error prone DNA polymerase fill gap and create mutations
Antibody Generation (Class Switching)
- Happens in constant region
- Allows dif daughter cells from same B cell produce antibodies of dif isotypes or subtypes
- Requires genetic recombo event
