Chapter 4 Flashcards
All non-self antigens are immunogens. True or false?
False. For example, some people are allergic to penicillin, while some are not.
What is an antigen versus immunogen?
Antigen = any agent capable of binding to immune components, such as B and T cells. May or may not elicit immune response
Immunogen = any agent capable of inducing immune response. All are antigens
Are haptens immunogens and/or antigens?
Haptens are antigens, but not immunogens by themselves unless bound to carrier protein
What are the 2 functional properties of antigens?
- Immunogenicity
- Reactivity: can react with immune cells
Which molecular weight (MW) compounds are immunogenic? Which MW compounds are not?
Greater than 6000 Daltons = immunogenic
Less than 1000 Daltons = NOT immunogenic
Give examples of haptens
Penicillin, aspirin, dander, progesterone, cosmetics
Give examples of complete antigens (greater than 6000 Daltons)
albumin and tetanus toxoid
Which is more immunogenic? A homopolymer of 50 kDa or copolymer of 40 kDa? Why?
Copolymer of 40 kDa is more immunogenic because it has more complexity than the homopolymer.
Is the homopolymer of glutamic acid of Bacillus anthracis immunogenic?
No, because it is not very complex and also resembles host components
Why are D-isomers not immunogenic?
Because the body only recognizes L-isomers. So, D-isomers can sneak away unnoticed and do not get degraded by enzymes
Which cell type degrades antigen? How?
APCs process the antigen and present them on silver platter for helper T cells
What two aspects comprise a likely non-immunogenic substance?
- Chemically simple
- low MW
What factor determines what we’ll be allergic to?
Mostly genes, some environmental factors
____% of drug allergies that result in death are due to _______
97%
Penicillin
Factors that contribute to immunogenicity? Describe in detail
- Dosage (number of minimum doses needed to elicit immune response)
- Route of administration of antigens (IV injection goes to spleen, subcutaneous injection goes to local lymph nodes and Langerhans (tissue resident macrophages in epidermis, oral is GI route that leads to intestinal response, intranasal route can elicit allergic reactions)
What is the difference between naive and effector B and T cells?
Naive B and T cells are mature and immunocompetent, but have NOT yet encountered antigen
Effector B and T cells are mature, immunocompetent, and have encountered antigen
Do B cells activate naive T cells? What is their role?
No, B cells do NOT activate naive T cells. They present antigen to helper T cells to assist own (B cell) activation
How is a B cell activated?
A B cell activates when antigens bind to its BCR and cross-link the B cells either in a chain or lattice
What happens to cross-linked Ag-receptor complexes?
They undergo receptor-mediated endocytosis. This incites clonal selection, then proliferation and differentiation into effector cells
What does it mean to be a “sensitized” person?
It means that mast cells have cross-linked to allergens
What do most clonally selected B cells differentiate into?
Most clones cells become plasma cells. Some become memory cells. Some clones stay behind as reserve cells in case something bad happens in the future
Where do antibodies circulate?
Blood or lymph
Describe plasma cells and their antibody secretion
They secrete 2000 Ab/s for 4-5 days, then die
How is clonal selection initiated?
Naive lymphocyte first encounters Antigen and is selected for further development. IF correct signals present, then it will complete differentiation
Most B and T cell clones are _____ cells
Effector. Few remain as memory cells
How long do B and T memory and effector cells last?
They circulate for a long time
Primary targets of B and T cells?
B cell = extra cellular targets, such as bacteria, parasites, some viruses in extracellular fluid, fungi
T cell = intracellular pathogens, such as viruses and cancer cells
What are the effectors of B and T cells?
B = plasma cells
T = helper, cytotoxic, and regulatory
What are the two types of inactive/naive T cells called? What do they differentiate into once they are effectors?
Naive = CD4 and CD8
Effector = CD4 become helper or regulatory T cells. CD8 become cytotoxic T cells
Role of helper T cells?
-Activate B cells and other T cells
-Activate macrophages
-Direct adaptive immune response
-some become regulatory T cells to suppress overactive immune response
-can become memory T cells
Role of CD8 T cells?
-Directly destroy foreign antigens by punching pores into them
-Can become memory T cells
Where is the highest naive B cell concentration found?
Red bone marrow
What are the primary and secondary immunizations/responses?
Primary = first exposure to antigen
Secondary = second exposure and is accompanied by faster and stronger immune response
Secondary response is also called ______. Which memory T cell populations are present?
Memory or anamnestic response. Central memory and effector memory T cells. Central memory T cells form limited effector function but offer long-term protection. Effector memory T cells offer full effector function but short-term protection
Where are central memory and effector memory T cells found?
Tcm = lymph nodes
Tem = peripheral tissues
Of carbs, lipids, nucleic acids, and proteins, which are immunogenic or not?
Proteins are the most immunogenic. Lipids and nucleic acids are not immunogenic by themselves unless conjugated to carrier protein
Which type of antigen has many epitopes of same specificity? Immunogenic?
Polysaccharides and homopolymer. Not very immunogenic
True or false: T cells respond to full antigens randomly roaming around in lymph nodes or blood
False. They only respond to processed fragments on APCs
Which cells express MHC I and MHC II?
MHC I = all nucleated cells (so no RBCs)
MHC II = APCs (DCs, macrophages, and B cells)
Describe MHC I glycoproteins
-Bind endogenous antigen (such as virus)
-Recognized by CD8 T cells
-Expressed as self-antigens in normal cell OR non-self antigen in infected/abnormal cell
-Inform CD8 of foreign microbes hiding in cells but ignore self-antigens
Describe MHC II glycoproteins
-Bind fragments of exogenous antigens that have been phagocytosed and displayed by APC
-Activate CD4 helper T cells -> tells helper T cells that help is required
APCs express which MHC class?
Both MHCI and II because are nucleated. APC’s exclusively express MHC II
Do polysaccharides activate T cells?
No because no internal epitopes present
What is the agretope?
Protein that binds MHC class
What do CD4 cells help to do?
They stabilize the interaction between MHC class II and epitope
How many amino acids do B cells recognize?
5-7 aa
How many amino acids to T cells recognize?
8-15 aa
Difference between sequential and non-sequential amino acids?
Sequential aa = aa are right next to each other (e.g., aa 4-10)
Non-sequential aa = aa next right next to each other (e.g., aa 4-8, 15-20 make one epitope)
Which protein example shown in class has sequential epitopes?
Sperm whale myoglobin
Which example protein shown in class has non-sequential epitopes?
Chicken egg lysozyme
