Primers to Immunology Major Concepts (Lecture 6)

Question 1

Which innate immune cells are non-phagocytic? (i.e. release inflammatory mediators)

Answer 1

»Basophils
»Mast cells
»Eosinophils
»Natural killer (NK) cells

Question 2

Which innate immune cells are phagocytic and release inflammatory mediators?

Answer 2

»Neutrophils
»Monocytes
»Macrophages

Question 3

Which cells are Phagocytic Cells?

Answer 3

Phagocytic cells – immune cells capable of phagocytosis – a process by which cells engulf large particles such as microbes.

» Neutrophils – the most abundant circulating white blood cells capable of phagocytizing and digesting microbes.
» Monocytes – circulating white blood cells which are
precursor cells for tissue macrophages.

» Macrophages – tissue residing phagocytic cells derived from monocytes. Infection-activated macrophages phagocytize and kill pathogens and secrete inflammatory mediators.

In bone marrow and released in circulation (monocytes).
They got to certain locations in precursor forms. Find
inflammation.

Question 4

Which are non-phagocytic cells?

Answer 4

» Basophils – blood circulating granulocytes (contain
granules in cytoplasm) which may contribute to
immediate hypersensitivity reactions (allergy).

» Mast Cells – tissue-residing cells involved in allergic
reactions. Contain numerous granules filled with
inflammatory mediators which being released trigger
the immediate hypersensitivity reactions.

» Eosinophils – circulating granulocytes which are
important in defense against extracellular parasites.
Contribute to allergic diseases (late phase reactions).

» Natural Killer (NK) Cells – a subset of lymphocytes
involved in innate responses. Recognize and kill
abnormal cells such virus-infected cells or tumor cells.

Question 5

What are hummoral components of Innate Immunity?

Answer 5

» Complement – a system of serum and cell surface proteins which upon
activation generate an important defense mechanism. Activation of
Complement results in a cascade of enzymatic reactions that produce
inflammatory mediators and opsonins (molecules attached to microbes).

» Acute-phase proteins – plasma proteins which concentration is
increased in response to inflammation (example: C-reactive protein).

» Cytokines - a large family of low-molecular-weight soluble proteins
involved in regulating cellular activity, particularly within the immune system.

» Chemokines – a large family of chemotactic cytokines which regulate the
transit of leukocytes from blood into tissues.

Question 6

What are Acquired Immune Responses?

Answer 6

– Antigen (Ag) – any molecule that provokes an immune response.
– Acquired immunity involves proliferation of antigen-specific B
and T cells, which occurs when the surface receptors of these
cells bind to antigen.

– Antibody (Ab) – a type of protein molecule that is also called
immunoglobulin. It is produced by B cells and exhibits a high
degree of specificity to Ag.

– T cell receptor (TCR) – an antigen receptor on cell membrane of T lymphocytes that recognizes foreign peptides presented by
Ag-presenting cells.

Question 7

What cells are important in aquired immunity?

Answer 7

CELLS INVOLED:
– Antigen-presenting cells (APC) display the antigen to
lymphocytes and collaborate with them in the response to the antigen.
– B cells secrete immunoglobulins, the antigen-specific
antibodies responsible for eliminating extracellular
microorganisms.
– T cells – the cell type that mediates cell-mediated immune
response of adaptive immunity. T cells are matured in the
thymus and circulate in the blood. Once activated by specific
antigen, T cells are recruited to a peripheral site (“gate of
infection”).
T and B lymphocytes are central in adaptive immune
response.

Question 8

What is the difference between gram positive and gram negative bacteria?

Answer 8

Gram positive have a thick peptidoglycan layer that would trap violet dye.

Gram negative have a thinner peptidoglycan layer. They have a thicker lipopolysaccharide (LPS) leaflet.

Question 9

Name 2 intracellular bacteria.

Answer 9

**Mycobacterium tuberculosis **

Tuberculosis, leprosy
Macrophage activation resulting in granulomatous inflammation and tissue destruction

Legionella pneumophila

Legionnaires’ disease
Cytotoxin lyses cells and causes lung injury and inflammation