MCB 3020C Lecture Notes - Lecture 30: Clonal Deletion, Immunogenicity, Hapten

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17 Jan 2020

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Specificity: immune cells have surface receptors that interact with individual antigens. Memory: the first antigen exposure induces multiplication of antigen-reactive cells, resulting in multiple copies, or clones. After a subsequent exposure to the same antigen, the immune response is faster and stronger due to the larger number of responding cells. Positive selection: t cells that recognize mhc peptides are retained. Negative selection: t cells that pass the positive selection and strongly bind to self-antigens are selected against. Clonal deletions: more than 99 percent of t cells that enter the thymus do not survive the selection process, remaining t cells react strongly with foreign antigens. Immunogens and antigen binding: antigens are substances that react with antibodies or tcrs, not all antigens are immunogens (substances that induce an immune response) Antibodies do not interact with an entire antigen, but only with a distinct portion of the molecule called an antigenic determinant or epitope.

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indicate whether you think the statements are true or false, and explain your reasoning. In each of your answers, provide 1-2 specific examples that support your position. (Each of your four answers is worth five points):

A) Memory cells require fewer distinct signals to be activated than naiÌve cells require.

B) Both B cells and T cells undergo âclonal selectionâ after they are activated by antigen.

C) A B cell is only able to present antigen to a T cell that includes the epitope to which the

B cellâs receptor bound.

D) T cells can recognize peptide antigens in the context of MHC I and MHC II regardless of

whether they are Thelper or Tcytotoxic cells.

E) B cells and T cells can both still make productive antigen receptors via V(D)J

recombination even if no P-nucleotides are introduced during the process.

F) Allelic exclusion takes place when a naiÌve T or B cell encounters its specific non-self antigen for the first time and determines whether or not to become activated.

G) B cells have more chances to make a productively rearranged antigen receptor than T cells do.

H) A majority of immature T cells developing in the thymus will survive both positive and negative selection.

I) The reason why T cells are the only type of white blood cell that requires maturation in a specialized organ outside the bone marrow is because they are the only ones that must have antigen processed and presented to them before they can be activated.

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1. Why is the process of gene rearrangement used in creating antibodies and T-cell receptors (TCRs) so important?

A. This is how our systems produce memory of pervious exposures, a key trait in adaptive immune responses.

B. Without it, we would need a single gene for every antibody and TCR required to mount all the possible responses need ed during our lives

C. interactions with antigens stimulate cells to initiate these processes, building the best and strongest response possible to the antigen

D. this is the same DNA altering process that leads to cancer. Understanding it leads to better treatments for cancer

2. Which of the following is NOT an antimicrobial substance?

A. keratin

B. Lysozyme

C. Defensins

D. Lactoferrins

E. Peroxidases

3. Which of the following is NOT an outcome of fever?

A. Direct destruction of microbes

B. increased release of pro-inflammatory cytokines

C. increased production of lymphocytes

D. increased phagocytic killing by leukocytes

E. increased production of interferons

4. Which of the following pattern recognition receptors is/are anchored in the host cell membrane?

A. Only C-type lectin receptors (CLRs)

B. Only RIG-like receptors (RLRs)

C. TLR and CLRs

D. Only toll-like receptors (TLRs)

E. NLRs and RLRs

F. Only NOD-like receptors (NLRs)

5. Fever allows the body to fight microbial invaders by which of the following mechanisms?

A.Fever plays all of these roles in the body

B. Fever prevents microbes with lower optimum temperatures from growing, giving the immune system time to eliminate those cells

C. Fever increases the inflammatory response, but reduces the production of interferons unless the invader is a dsRNA virus

D. A moderate fever reduces the inflammatory response but stimulates phagocytic activity in neutrophils and eosinophils

E. Fever increases the multiplication of lymphocytes and enhances the release of substances that attract basophils that then engulf the microbial invader

6. According to the clonal selection theory

A. Each B cell is already programmed to produce a specific antibody

B. B cells producing autoantibodies are eliminated in the thymus

C. Self-reactive T cells are killed in the thymus AND B cells producingautoantibodies are eliminated in the thymus

D. Seld-reactive T cells are killed in the thymus

7. Apoptosis

A. is a form of programmed cell death AND is induced in target cells by effector T cytotoxic cells

B. refers to the transformation of B cells into plasma cells

C. is induced in target cells by effector T cytotoxic cell AND results specifically in T cell death

D. results specifically in T cell death AND refers to the transformation of B cells into plama cells

How did inoculation with cowpox generate immunological memory and provide protection against smallpox? Did cross-reactivity play a role?

How did Pasteurâs work with attenuated (weakened) bacteria further our understanding of the role vaccination can play?

What are the three characteristics that define an adaptive immune response? Briefly define each of the characteristics.

Define primary versus secondary immune response.

Whatâs the difference between totipotent, pluripotent, multipotent and oligopotent when evaluating cell differentiation capacity?

What is hematopoiesis?

What cell types are derived from myeloid versus lymphoid progenitor cells? Describe the function of each WBC type.

What is clonal selection?

What role do antibodies play with regard to antigen recognition and immune defense that is different from what Tcrs provide?

As described in class generally understand the outcome of B cell, Th cell, and Tc cell activation. Understand that these cells can differentiate into effector (plasma cells, cytokine producing Th cells and CTLs) or memory cells.

Understand how granzymes and perforins play a role in apoptosis.

Which types of cells typically express MHC Class II? Do these cell types also express MHC Class I, and if so why?

With regard to Tc and Th cells, what kinds of peptide antigens (think about exogenously versus endogenously derived antigens) are recognized?

Be able to show cooperation between Tc, Th and B cell responses (refer to class notes).

What is the overall role of MHC Class I and II?

What is ADCC and what cell types are involved?

Understand and be able to provide examples highlighting the cooperation between innate and adaptive immunity. Note: ADCC and dendritic cell and macrophage interactions with Th cells illustrate examples of innate/adaptive cooperation.

What are the primary lymphoid organs? What role do they play?

What role does the lymphatic circulatory system play in immune defense?

Whatâs the difference between plasma, ISF, and lymph?

Whatâs the difference between afferent and efferent lymphatic vessels?

How is lymph ultimately delivered back to blood?

Define extravasation. Why is this important?

What are HEVs and what role do they play?

What are the secondary lymphoid tissues/organs?

What role do lymph nodes play?

What role does the spleen play?

What is Leukocyte Adhesion Deficiency?

Whatâs MALT and its role?

What is the inflammatory response and what are characteristics associated with inflammation?

What role does histamine play in the inflammatory response?

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MCB 3020C Lecture Notes - Lecture 30: Clonal Deletion, Immunogenicity, Hapten

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