30 Questions
Which of the following accurately describes the process of T cell activation?
T cell activation occurs when the T cell receptor (TCR) recognizes antigens presented by MHC class I or II molecules, leading to T cell proliferation and differentiation.
What is the key difference between T helper cell subsets Th1, Th2, Th17, and Treg?
Each subset has distinct cytokine profiles and plays different roles in immune responses.
What is the primary role of cytotoxic T cells in the immune response?
Cytotoxic T cells recognize and eliminate virus-infected or abnormal cells through the release of cytotoxic molecules.
Which of the following is a key mechanism for achieving self-tolerance in T cells?
Central Tolerance
What disorder is associated with a deletion on chromosome 22 and leads to poor T cell production?
DiGeorge syndrome
Which type of T cells are involved in direct killing of target cells?
CD8+ T cells (Cytotoxic)
Which rare disorder is typically fatal in the first 2 years of life and is characterized by low/absent T/B cells?
Severe Combined Immunodeficiency (SCID)
Where does the differentiation of T cells into effector cells occur?
Lymph nodes
What is the main function of Naïve T cells?
Activation of B cells
Which subset of CD4+ T cells is expected to activate neutrophils?
Th17
Which T cell subset is responsible for secreting IL-5 and activating eosinophils and mast cells?
Th2
Which T cell subset is primarily associated with the secretion of INF-γ?
Th1
What is the main function of Helper T cells (Th)?
Provide help to B cells and macrophages
Where does T cell development occur?
Thymus
What is the function of T cell co-receptors CD4 and CD8?
Are involved in positive selection
Where do B cells originate from?
Bone marrow
What is the primary function of plasma cells?
Produce antibodies
What triggers B cell activation?
Antigen recognition
What is the primary location for B cell development?
Bone marrow and spleen
What is the function of the Fab portion of antibodies?
Contains the antigen binding site
What is the role of naïve B cells when they leave the bone marrow?
They have a functioning BCR prior to antigen exposure
Which of the following cells have binding sites for immune cells?
Mast cells, basophils, and eosinophils
Which process leads to an increase in antibody affinity with prolonged exposure to an antigen?
Affinity maturation
Which antibody isotype is the most abundant in serum and carries out various antibody functions including opsonization, ADCC, neutralization, and complement activation?
IgG
Which immunodeficiency disorder is characterized by low antibody levels of IgG, IgM, and IgA, and commonly presents with recurrent infections of the lungs and gastrointestinal tract?
Common Variable Immune Deficiency (CVID)
Which immunodeficiency disorder is the most common, resulting in the failure of B cells to differentiate into IgA producing plasma cells, and at least one-third of patients are asymptomatic due to IgM compensation?
Selective IgA Deficiency
Which immunodeficiency disorder is caused by a mutation in a protein involved in B cell development, leading to the absence of B cells and recurrent bacterial infections?
X-linked agammaglobulinemia (XLA)
Which immunodeficiency disorder is characterized by low/absent T/B cells and is typically fatal in the first 2 years of life?
Severe Combined Immunodeficiency (SCID)
Which immunodeficiency disorder is associated with a deletion on chromosome 22 and leads to poor T cell production?
DiGeorge Syndrome
Which immunodeficiency disorder is most commonly asymptomatic due to IgM compensation?
Selective IgA Deficiency
Study Notes
Key Roles of T-Cells in Adaptive Immune System
- T-cells are part of the adaptive immune system and have two main functions: Helper T cells (Th) and Cytotoxic T cells (CTL).
- T cells must interact with other cells and have a unique T cell receptor (TCR) with a diverse repertoire.
- TCR recognizes antigens bound to Major Histocompatibility Complex (MHC) on cells.
- T cells generate memory cells that can live for over 20 years.
- T cell development occurs in the thymus, where immature T cells undergo development and selection processes.
- Checkpoints are required to ensure the selection of appropriate T cells, including positive and negative selection.
- Positive selection occurs when TCR interacts with self-MHC, and negative selection protects against autoimmunity.
- Naïve T cells circulate in lymph nodes to await antigen exposure.
- TCR is composed of alpha and beta chains, each with variable and constant regions.
- T cells have co-receptors CD4 and CD8 that are involved in positive selection.
- T cells have effector functions, including direct killing by CTL and help given to B cells and macrophages by Th cells.
- APCs, including dendritic cells, macrophages, and B cells, are involved in T cell activation and response to antigens.
Understanding Antibody Functions
- Macrophages, mast cells, basophils, NK cells, neutrophils, and eosinophils all have binding sites for immune cells.
- Isotype switching allows B cells to produce different antibody isoforms (IgG, IgA, IgE, IgD) with the same antigen-binding site but different constant heavy chain regions.
- Isotype switching is induced by CD40-CD40L interaction and T helper cell-released cytokines.
- Affinity maturation is the process by which antibody affinity increases with prolonged exposure to an antigen.
- Antibody effector functions include protection through IgG, IgE, and IgM.
- Antibody neutralization of microbes and toxins occurs by binding and making them too bulky to enter cells.
- Opsonization marks pathogens for phagocytosis by coating them with antibodies, facilitating recognition by phagocytes.
- Complement activation involves antigen and complement recognition sites on antibodies, leading to the activation of the complement cascade.
- Antibody-dependent cellular cytotoxicity involves NK cells and other leukocytes binding to antibody-coated cells and destroying them.
- Eosinophils and mast cells mediate reactions against large pathogens through IgE antibodies.
- There are five types of heavy chains (gamma, alpha, mu, delta, epsilon) leading to the formation of IgG, IgA, IgM, IgD, IgE.
- IgG is the most abundant antibody isotype in serum and carries out all known antibody functions including opsonization, ADCC, neutralization, and complement activation.
Test your knowledge of the key roles of T-cells in the adaptive immune system with this quiz. Explore the functions of Helper T cells (Th) and Cytotoxic T cells (CTL), T cell receptor (TCR) recognition of antigens, T cell development and selection processes, co-receptors CD4 and CD8, and effector functions. See how much you know about T cell activation and response to antigens by antigen-presenting cells (APCs).
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