Chapter 17 Microbiology Flashcards
What is innate immunity?
defenses against any pathogen
What is adaptive immunity?
induced resistance to a specific pathogen
Bacterial toxins generate the production of _____ in the serum
Antitoxins
Antitoxin sera mixed with toxin could be given to prevent what disease that was common in childhood death?
Diphtheria
Paul Ehrlich’s contribution to microbiology:
Body produces excess antitoxins which last beyond exposure. Thought this was immunization.
Michael Heidelberger’s contribution to microbiology:
Discovered that antigens of pneumococcus are polysaccharides
Discovered that antibodies are proteins
Gerald Edelman’s contribution to microbiology:
Determined general structure of antibodies
Susumu Tonegawa’s contribution to microbiology:
Determined that genes in B cells produce different antibodies to virtually any antigen
Serology
The study of reactions between antibodies and antigens
Antiserum
The generic term for serum that contains antibodies
What are globulins?
Serum proteins
Gamma globulin
serum fraction containing antibodies
Immunoglobulins (Ig)
Antibodies
What is hematopoiesis?
Production of blood cells
Antigen (Ag)
substance that causes the body to produce specific antibodies or sensitized T cells
Antibodies (Ab)
Interact with epitopes or antigenic determinants
Hapten
antigen too small to be recognized by the immune system that can be recognized when combined with a carrier protein
How are haptens linked to carrier proteins?
penicillin is not immunogenic on its own. It is covalently attaches to proteins in the blood and the combo makes it recognizable by the immune system
Antibody monomers have how many protein chains?
Four. Two heavy chains and two light chains. Make Y shaped structure
How are heavy and light chains joined?
Disulfide bonds
Variable regions
On the ends of heavy and light chains to bind to epitopes
Fc region
Stem of Y shaped structure that crystalized in cold storage
Why are Fc regions important?
Fc regions of adjacent antibodies can bind complement if left exposed after both antigen binding sites attach to antigen
Fc region may bind to a cell to leave the binding sites of adjacent antibodies free to react
IgG antibodies
monomer, 80% of serum antibodies, fix complement, cross placenta, enhance phagocytosis; neutralize toxins and viruses
Half life=23 days
IgM antibodies
Pentamer, 5-10% serum antibodies, fix complement, in blood lymph and B cells,
agglutinates microbes; first Ab produced in response to infection
Half life=5 days
IgA antibodies
Dimer, 10-15% serum antibodies, in secretions, mucosal protection
Half life=6 days
IgD antibodies
Monomer, 0.2 % of serum antibodies, in blood, lymph and B cells
Half life=3 days
IgE antibodies
Monomer, 0.002% of serum antibodies, on mast cells, basophils and in blood, allergic reactions; lysis of parasitic worms
Half life= 2 days
What is unique about B cells class switching?
A single B cell can produce different classes of antibodies over time B cells can switch Ig class and keep antigen specificity
What does DNA recombination do in Ig classes?
Causes a switch from one Ig class to another
What is the fate of randomly generated B cells?
Autoantibodies are eliminated
All mature B cells have antibodies on their surface
Those that proliferate may become plasma cells or memory B cells
What do T cells activate?
Activate B cells to secrete Ab
B cell is activated to secrete antibodies if it and T cell can recognize same antigen
What is clonal deletion?
Eliminates harmful B cells
What is clonal selection?
Expands activate B cells
What occurs when Ab meets antigen?
Agglutination Opsonization Complement fixation Antibody-dependent cell mediated immunity Neutralization
Agglutination
Reduces the number of infectious units to be dealt with
Opsonization
Coats antigen with antibody enhances phagocytosis
Complement fixation
Causes inflammation and cell lysis
Antibody dependent cell mediated immunity
Antibodies attached to target cell cause destruction by macrophages, eosinophils and NK cells
Neutralization
Blocks adhesion of bacteria and viruses to mucosa, blocks attachment of toxin
T Cells and Cellular Immunity
T cells mature in the thymus
T cells respond to antigen by T cell receptors, T cell version of antibodies
T cells require antigen presenting cells (APCs)
T cell receptors must interact with MHC molecules
Antigen presenting cells
B cells
Dendritic cells
Macrophages
Efficient at ingesting and processing antigens and presenting them on their surface
MHC and HLA
Mouse: Major Histocompatibility Complex
Human: Human Leukocyte Antigens
Transmembrane cell surface proteins that hold antigens for presentation
Class I and Class II
Differs slightly among individuals of a species
Responsible for tissue rejection in transplants
T cells types
T Helper Cells (TH) (CD4+)-activate antibody response
T Cytotoxic Cells (Tc) (CD8+)- directly target host cells
T Regulatory Cells (TReg)- keep the immune system in check
T helper cells
CD4+ r T cells
work by activating B cells
TCRs recognizing antigens with MHC class II on antigen presenting cells
TH cells produce cytokines and differentiate into Th1, Th2, Th17, memory T cells
What does TH1 produce?
IFN-γ (gamma interferon), which activates cells related to cell-mediated immunity, macrophages, and antibodies; effective against intracellular pathogens
What do TH2 cells activate?
eosinophils and B cells to produce IgE; important in allergic reactions; effective against helminths (worms)
What do TH17 cells produce?
large amounts of cytokine IL-17, recruit neutrophils, and work against certain extracellular bacteria and fungi
How are T Helper cells activated?
- APC encounters antigen
- APC processes antigen protein into short peptide
- APC presents antigen fragment with MHC II
- TH cell encounters APC presenting antigen
- TCR recognizes antigen fragment with MHC II
- co-stimulatory signal is needed to activate T cells that have not previously encountered antigen
- TH cell is activated and produces cytokines
What are antigen presenting cells?
- B cells, dendritic cells, activated macrophages
- Digest antigen
- Present fragments on APC surface with MHC class II
What are M cells on Peyer’s patch?
Pathogens entering the gastrointestinal or respiratory tracts pass through:
- M (microfold) cells over
- Peyer’s patches, which contain APCs
What are cytotoxic cells?
CD8+ or TC cells
Target cells are “self” with endogenous antigens
Activated into cytotoxic T lymphocytes (CTLs)
MHC class I molecules are on all cells of the body
CTLs recognize antigen with MHC class I
Induce apoptosis in target cell
CTL releases perforin and granzymes
Immunotherapies target inhibitory regulation of T cells such as ____ that can___
anti Pd1 antibodies that can cure incurable cancers
What are T regulatory cells?
TReg cells are similar to TH cells
-Have CD4 and CD25 on their surface
-Suppress T cells that act against “self” antigens
to block their potentially destructive activity
TCRs that are like autoantibodies
What are natural killer cells?
Extracellular killing by the immune system
NK cells are granular leukocytes
destroy any cells that don’t express MHC I
kill virus-infected and tumor cells
attack parasites
What is ADCC?
Antibody-dependent cell-mediated cytotoxicity
antibodies stimulate NK and other cells to kill
Require Fc receptors on the killing cell
What are cytokines?
Cytokines are chemical messengers Overproduction leads to “cytokine storm” signaling gets out of control can cause significant damage to tissues part of pathology of many diseases influenza graft-versus-host disease sepsis
What is immunological memory?
-Antibody titer is the amount of antibody in serum
-Primary response occurs after initial contact with antigen
-Secondary or memory (anamnestic) response occurs after second exposure
Its why vaccination works
what are the types of adaptive immunity?
-Naturally acquired active immunity Resulting from infection -Naturally acquired passive immunity Transplacental or via colostrum -Artificially acquired active immunity Injection of Ag (vaccination) -Artificially acquired passive immunity Injection of Ab
