40 Questions
Where do B-cells mature?
Bone marrow
Which organ serves as the major site of adaptive immune responses?
Spleen
What is the role of the lymphatic system and lymph nodes?
Blood-borne infection filtration
Which terminology refers to a substance that enhances T-cell and B-cell activation?
Adjuvant
Where does T-cell development primarily occur?
Thymus
What is the primary function of neutrophils in the immune system?
Participate in immunological surveillance
Which of the following cells is known for secreting histamine during allergic responses?
Mast cells
What is the main role of dendritic cells in the immune system?
Initiate adaptive immune responses
Which of the following cells acts as effector cells in cell-mediated immunity?
Dendritic cells
In inflammatory responses, which cell type primarily responds to injury and infection?
Neutrophils
What is the most abundant type of leukocyte?
Neutrophils
Which cell type is known for its high local release of reactive oxygen/nitrogen species and cytotoxic granules?
Neutrophils
Which immune cell type acts as sentinels of the immune system and react to danger stimuli?
Dendritic cells
Which immune cell type is specialized for responding to viral infections and secretes Type I Interferon?
Plasmacytoid dendritic cells
Which cells are considered the 'bridge' between innate and adaptive immunity?
Dendritic cells
Which term refers to the process of attaching opsonins to microbial surfaces to target them for phagocytosis?
Opsonization
What is the term used to describe local swelling and redness at the site of an immediate hypersensitivity reaction?
Wheal-and-flare reaction
Which type of antibody is determined by the form of heavy chain present?
Isotype
What type of cells are responsible for stimulating leukocyte chemotaxis?
Mast cells
Which term refers to unresponsiveness of the adaptive immune system to antigens?
Tolerance
Which type of cells are recruited to, or resident in, sites of infection and are responsible for recognizing, ingesting, and killing microbes?
Eosinophils
Which type of cell matures from circulating monocytes and is resident in most tissues, with a unique naming scheme based on anatomical location?
Dendritic cells
Which type of cell is characterized by large numbers in connective tissue and the submucosa of the gastrointestinal tract?
Mast cells
Which type of cell is primarily responsible for immediate recognition of invaders and is recruited to sites of infection along with neutrophils?
Eosinophils
Which type of cell is NOT mentioned in the text as being part of the immediate recognition of invaders at sites of infection?
Basophils
Which of the following is NOT a mechanism of action of antimicrobial peptides in innate immunity?
Reactive oxygen/nitrogen species
What is the primary function of the Complement System in innate immunity?
Lysing cells, bacteria, and viruses
Which pathway of the Complement cascade is triggered by the binding of mannose-binding protein to terminal mannose residues on microbial surfaces?
Lectin pathway
What is the central component that attaches to microbes and activates downstream complement proteins in the Complement system?
Complement factor C3
Which application involves Eculizumab, a monoclonal antibody targeting a specific complement factor?
Treating paroxysmal nocturnal hemoglobinuria
What is the main function of neutrophils in the immune system?
Destroy infected host cells by releasing granule contents
How do mast cells contribute to the immune response?
Produce cytokines similar to T lymphocytes
What is the role of basophils in the immune system?
Target tumors expressing low MHC class I
How do eosinophils differ from NK cells in recognizing target cells?
Recognize infected cells based on inhibitory receptors for MHC I alleles
What distinguishes dendritic cells from NK cells in their immune function?
Establish short interactions with other immune cells
Why are neutrophils, eosinophils, and basophils collectively referred to as granulocytes?
Based on the presence of cytoplasmic granules visible under a microscope
Which immune cell type is primarily responsible for guiding later T cell responses?
Mast cells
How do basophils differ from neutrophils in their immune functions?
Target tumors expressing low MHC class I
How do eosinophils contribute to eliminating cellular reservoirs of infection?
Kill infected host cells by releasing granule contents
Which immune cell type is known for distinguishing between infected and uninfected cells based on inhibitory receptors for MHC I alleles?
NK cells
Study Notes
Immune System Components
- Chemokine: a family of structurally homologous low-molecular weight cytokines that stimulate leukocyte chemotaxis
- Epitope: the specific portion of a macromolecular antigen to which an antibody binds
- Hybridoma: a cell line derived by fusion between a normal lymphocyte and an immortalized lymphocyte cancerous cell
- Isotype: one of five types of antibodies, determined by which of the five different forms of heavy chain is present
- Opsonization: the process of attaching opsonins, such as IgG or complement fragments, to microbial surfaces to target them for phagocytosis
- Tolerance: unresponsiveness of the adaptive immune system to antigens, as a result of inaction or death of antigen-specific lymphocytes, induced by exposure to antigens
Lymphoid Organs
- Bone Marrow: site of blood cell development, immune cell progenitors; spongy central cavity of bone; site of B-cell maturation
- Thymus: site of T-cell development; two-lobed organ divided by inner medulla and outer cortex; site for central tolerance; positive and negative selection
- Lymphatic System and Lymph Nodes: lymph-borne infection filtration; lymphatic vessels connect the lymphatic system; lymph nodes: encapsulated nodular aggregates of lymphoid tissues located along lymphatic channels throughout the body
- Spleen: blood-borne infection and dead cell filtration; highly vascularized abdominal organ; major site of adaptive immune responses; red pulp: composed of blood-filled vascular sinusoids lined by active phagocytes that ingest opsonized antigens and damaged red blood cells
Immune Cells
- Neutrophils: first responders to infection or trauma site; most abundant type of leukocyte (white blood cell = WBC); recruited from blood to infection site driven by chemotaxis; phagocytic; high local release of reactive oxygen/nitrogen species and cytotoxic granules
- Dendritic Cells: bridge between innate and adaptive immunity; respond to microbes by producing cytokines; "professional" antigen-presenting cells (APCs); major function
- Mast Cells: sentinels of the immune system; react to danger stimuli; present in skin and mucosal epithelium; abundant cytoplasmic granules; contents (e.g., vasoactive amines) released upon activation
- Macrophages: diverse functional potentials, depending on location and signals; two general functional classifications: M1 (inflammatory) vs. M2 macrophages (secrete growth factors and enzymes: tissue repair = “alternative macrophage activation”)
Innate Immunity
- Anatomic and physiologic barriers: skin, mucous membranes, lysozymes (mucous secretions and tears), stomach and vaginal pH, saliva, perspiration
- Cellular: cells in tissues and circulation; blood monocytes, PMNs (neutrophils), tissue macrophages (Kupffer and Langerhans cells), etc.
- Soluble and chemical mediators: plasma proteins, cytokines, complement factors, collectins
Complement System
- First discovery: augments opsonization and bacterial killing by antibodies
- Consists of many distinct plasma proteins; produced by liver; inactive in plasma and tissue until activated locally by exposure to: specific carbohydrate chains on microbial surface; Ag-Abs complexes; lectin binding to pathogen surface
- Functions: lyse cells, bacteria, and viruses; coat microbes: opsonins; promote phagocytosis; inflammatory mediators
- Nomenclature: designated by numerals and letters, some with more arcane names; peptide fragments denoted by small letters (a, b)
Cytokines
- Small peptides (25 kDa) released by a variety of cells; mediate many cellular rxns of innate (& adaptive) immunity
- Induce responses by binding specific receptors; autocrine, paracrine, endocrine
- Structurally diverse, grouped by structure, as are receptors
Learn about soluble mediators such as plasma proteins, cytokines, and complement factors, as well as the role of neutrophils as first responders in the immune system. Explore their functions, recruitment to infection sites, and release of reactive species and granules.
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