Immune System: Part 3 - Interactive Lecture

​Immune System: Part 3

Interactive Lecture

Multiple Choice

Where do immature T cells undergo the processes of positive and negative selection during their development?

• Bone marrow

• Thymus

• Lymph nodes

• Spleen

Multiple Choice

What is the main purpose of positive selection during T cell maturation?

• To eliminate T cells that bind too strongly to self-antigens

• To ensure T cells can recognize self-MHC molecules

• To stimulate antibody production

• To generate memory T cells

Multiple Choice

Which of the following best describes the main role of Helper T cells (CD4⁺)?

• Destroy virus-infected cells directly

• Secrete antibodies to neutralize antigens

• Release cytokines to coordinate immune responses

• Suppress immune activity to prevent autoimmunity

Multiple Choice

Cytotoxic T cells (CD8⁺) recognize antigens presented on which class of MHC molecule?

• MHC Class I

• MHC Class II

• MHC Class III

• Both Class I and II

Multiple Choice

What is the main outcome of clonal expansion following T cell activation?

• Generation of plasma cells that secrete antibodies

• Production of identical effector and memory T cells

• Elimination of self-reactive T cells

• Phagocytosis of pathogens by macrophages

Multiple Choice

Which pairing correctly matches a T cell subtype with its specialized function?

• Th1 cells — stimulate B cells to produce antibodies

• Th2 cells — enhance macrophage activity

• Regulatory T cells — suppress overactive immune responses

• Memory T cells — destroy infected host cells

Explanation

Regulatory T cells are a specialized subset of T lymphocytes that help maintain immune balance. Their primary role is to suppress excessive immune activity, which prevents tissue damage and autoimmune reactions.

Other T cell subtypes have different functions:

• Th1 cells mainly activate macrophages and cytotoxic T cells to fight intracellular infections.

• Th2 cells help B cells produce antibodies, especially IgE, and are involved in responses to parasites and allergens.

• Memory T cells do not directly kill infected cells but remain in the body to ensure a faster and stronger response to future encounters with the same antigen.

Because of these differences, only regulatory T cells have the distinct function of moderating immune responses and maintaining self-tolerance.

Multiple Choice

What is the main goal of central tolerance during B cell development?

• To enhance antibody diversity

• To eliminate self-reactive B cells before they enter circulation

• To activate mature B cells against pathogens

• To promote clonal expansion of effector cells

Multiple Choice

What happens to a B cell that binds strongly to self-antigen in the bone marrow?

• It receives T cell help and becomes activated

• It undergoes clonal deletion through apoptosis

• It becomes a plasma cell

• It differentiates into a memory cell

Multiple Choice

Which of the following correctly explains the role of T helper cells in B cell tolerance?

• They directly destroy self-reactive B cells

• They provide signals that prevent activation of self-reactive B cells

• They rearrange immunoglobulin genes to create new receptors

• They stimulate apoptosis in all immature B cells

Multiple Choice

Which type of antigen typically requires T-cell help for B cell activation?

• Polysaccharide antigen

• Lipid antigen

• Protein antigen

• Nucleic acid antigen

Multiple Choice

What role does the CD4⁺ helper T cell play during T-cell–dependent B cell activation?

• It secretes antibodies to neutralize antigens

• It provides cytokines and co-stimulatory signals for full B cell activation

• It suppresses the immune response

• It directly kills infected cells

Multiple Choice

During differentiation, what is the primary function of plasma cells?

• Present antigen to helper T cells

• Secrete large quantities of antibodies

• Provide long-term immune memory

• Undergo clonal deletion

Multiple Choice

How does T-cell–independent B cell activation differ from T-cell–dependent activation?

• It generates a slower but stronger immune response

• It produces extensive class switching and memory

• It requires MHC II presentation

• It produces a rapid but weaker response with limited memory