BSI 2 Lecture 8-10: Immunology Flashcards
What is responsible for the specificity of the acquired immune response?
Specific antigens
What allows the body to generate immunity against invading bacteria, viruses, toxins, and foreign tissues?
Lymphocytes
How do lymphocytes generate immunity?
1) Produce specific antibodies
2) attack and destroy the invader
What type of lymphocytes produce a humoral response by synthesizing circulating antibodies that target the invader for destruction?
B-lymphocytes
What type of lymphocytes produce activated “killer cells” that directly destroy the invaders?
T-lymphocytes
What are antigens recognized by?
Immunoglobulins (antibodies)
The different blood group antigens (A and B), are due to different ___________ on a surface glycoprotein.
Sugar residues
What do T-lymphocytes need to activate them specifically?
Antigen Presenting Cells
Define: Antigens
Molecules that are identified as foreign and produce an immune response
What is the name for the repeating/reoccurring molecular groups?
Epitopes
Where are B-cells produced?
Prior to birth they are processed in the liver, after birth they are made in the bone marrow
Where are lymphocytes activated?
In peripheral lymphoid organs
What are the functions of B-cells?
1) Initiate antibody-mediated immune responses
2) Transform into plasma cells, which secrete antibodies
3) Present antigens to helper T cells
What is the function of a cytotoxic T cell (CD8 cells)?
Bind to antigens on plasma membrane of target cells and directly destroy the cells
What is the function of Helper T cells (CD4 cells)?
Secrete cytokines that help to activate B cells, T cells, NK cells, and macrophages
What are the functions of NK cells?
1) Bind directly and nonspecifically to virus-infected cells and kill them
2) Function as killer cells in antibody-dependent cellular cytotoxicity
Where are Plasma cells produced?
In peripheral lymphoid organs; differentiate from B cells during immune responses
What is the function of plasma cells?
To secrete antibodies
Can B-cells produce antibodies?
No, they have to transform into plasma cells in order to secrete antibodies
What type of cell can’t present a recognition to the a cytotoxic T cell?
Red blood cells
What is the power house of acquired immunity?
Lymphocytes
What filters the lymph?
Lymphnodes
What filters blood?
Spleen, thymus, bone marrow, and liver
What are the two types of lymphocytes?
B-lymphocytes and T-lymphocytes
Where do these lymphocytes derive from?
Pluripotent hematopoietic stem cells
Where do nearly all lymphocytes reside?
In lymphoid tissues
Where do potential T-lymphocytes first migrate?
Thymus
Where are B-lymphocytes processed before birth?
Liver
Where are B-lymphocytes processed throughout life?
Bone marrow
Once in the thymus, T-lymphocytes divide rapidly and develop specific reactivity to how many antigens?
One
What is the most important thing that happens to T-lymphocytes while in the thymus?
They are checked to ensure that they do not respond to any of the body’s own tissues or “self-antigens”
If the thymus is responsible for processing T-lymphocytes, can it be removed?
Yes, it processes prior to and right after birth. So you don’t have to have it.
What happens when a lymphocyte comes in contact with the specific antigen that it has been programmed to respond to?
It causes rapid cell division which produced increased numbers of lymphocytes with identical specificity
How is a great diversity of antigens achieved despite being encoded for by only 100-1000 genes?
Shuffling of gene segments during processing
How can macrophages, B-cells, and dendritic cells activate lymphocytes?
After engulfing a pathogen, it can present the antigen of the pathogen directly to the correct lymphocyte
What do macrophages secrete to promote further reproduction and growth of lymphocyte clones?
Interleukin-1
What are the three events required for activation of Helper T-Lymphocytes?
1) Presentation of an antigen bound to MHC II protein on APC or B-cell
2) Binding of matching non-antigenic proteins on Helper and APC or B-cell
3) Secretion, by APC or B-cell, of cytokines including IL-1 and TNF which act on the Helper lymphocyte
T-lymphocytes only respond when the antigen is bound to special surface molecules called ________
Major Histocompatibility Complexes (MHCs)
What are the three major types of APCs?
Macrophages, B-lymphocytes, and Dendritic cells
How many classes of MHC proteins are there?
2
MHC1 presents to what lymphocyte?
Cytotoxic T-lymphocytes
MHC2s present to what lymphocyte?
Helper T cells
Where are T-cells produced?
They are produced in the bone marrow and them processed in the thymus
What do Helper T-cells do?
They secrete lymphokines that enhances the activation of processed B-lymphocytes
Without the enhancement form Helper T-cells, what would happen to the number of antibodies?
The number of antibodies secreted by B-cells would be insufficient, and the immune response wouldn’t be great
Can a B-cell act as an APC?
Yes, immunoglobulin receptors can bind with antigens to engulf them and present them on an MHC II protein
What are the steps of an activated B-cell becoming a plasma cell?
Activated B-cell –> lymphoblast –> plasmoblast –> plasma cell
What is the primary response?
When you are introduced to a pathogen for the first time and your body produces antibodies to mount an immune response
What is a secondary response?
This is a greater more rapid response because your body has been introduced to this pathogen before and it is recognized by memory cells. This is why immunizations are important.
Do all activated B-cells become plasma cells?
No, some turn into memory cells
About how long does it take the body to form an immune response to a new pathogen?
About a week with a low number of antibodies that are produced for a few days to weeks
How long does the body take to start a secondary immune response?
A few hours with a high number antibodies that are produced for a few months
Most antigens are ______ meaning they have two binding sites.
Bivalent
What does the constant portion of the antibody determine?
General properties like opsonization
What causes specificity at the binding site of an antigen?
Amino acids
What are the five classes of antibodies?
IgG, IgA, IgM, IgE, IgD
Which antibody (immunoglobulin) is the most numerous in the body?
IgG making of 75% of all antibodies
What is IgG responsible for?
Immune response in the thymus
What is IgA responsible for?
Immune function of mucus membranes
What is IgM responsible for?
Presented on B-cells/control of B-cells
What is IgE responsible for?
Allergy responses
What is IgD responsible for?
Co-expressed with IgM on B-cells
What are the 4 actions of antibodies?
1) Agglutination
2) Precipitation
3) Neutralization
4) Lysis
What is agglutination?
large invaders become bound together by antibodies and form clumps
What is Precipitation?
Linked molecules become so large they become insoluble
What is Neutralization?
Bind antibodies cover and therefore inactivate toxic sites
What is lysis?
Rupture cell membranes (usually requires amplification from the complement pathway)
What starts the Classic complement cascade?
A specific antigen/antibody (IgM or IgG) binding where the constant portion of the antibody binds to C1 and activates it
What is C3b responsible for?
Opsonization of bacteria
What complement factors activate mast cells and basophils?
C3a, C4a, and C5a
Which complement factor is responsible for chemotaxis of white blood cells (neutrophils and macrophages)?
C5a
What are the 4 types of T cells?
Helper, Cytotoxic, Suppressor, and Natural killer cells
What is the most numerous T-lymphocyte?
Helper T-lymphocytes
Why are Helper T-cells so important?
They activate both suppressor and cytotoxic T-cells, and stimulate C-cell growth into plasma cells
How do cytotoxic T-cells kill pathogens?
They puncture holes in their membrane with perforin proteins, and then they release cytotoxic substances into their targets
Where is the MHC I protein found?
On all nucleated cells
How are NK cells different than Cytotoxic T-cells?
They are not antigen specific and they do NOT use MHC proteins
What are the major cytokines from Helper T-cells that cause NK cells to proliferate and secrete their cell-killing hormones?
IL-2 and interferon-gamma
Do NK cells require IL-2 and interferon-gamma to be activated?
No, this is why they are also part of the innate immune response
In the general systemic effects of infection, which Interleukins are released?
IL-1, IL-2, IL-6, and TNF
What are some general responses from the systemic effects of infection?
1) increased WBC production
2) increased plasma fatty acids
3) increased amino acids
4) increased acute phase proteins
5) increased cortisol
What is Rheumatic fever?
When the body becomes sensitized to tissues in joints and heart valves after exposure to specific Streptococcal toxins
What is Multiple Sclerosis is probably due to?
A virus with similar antigenic properties to myelin
What happens with Poison Ivy toxin?
The initial exposure induces a mild response, but after repeated exposures the response becomes so extreme that healthy tissue is harmed
Allergic tendency is inherited and characterized by excessive _____ antibodies in the blood.
IgE
Inactive complement proteins are formed in the ________ and travel around in the ________ until activated.
Liver, bloodstream
