MIDTERM Lesson 2.4: The Immune System & Lymphoid Organs

Innate Immunity

Immediate and non-specific actions.

Physical Barriers

• Skin

• Mucous membrane of GIT, respiratory tract, and urogenital tract.

Receptors

• Tool-Like Receptors (TLRs)

• NK Cells

Adaptive Immunity

More specific, slower to respond and evolutionarily more recent development than innate immunity. (B & T lymphocytes)

• Production of memory lymphocytes.

Cytokines

Proteins that act as chemical messengers in the immune system.

• Helps to control inflammation in the body.

• Stimulates phagocytosis.

• Increased mitotic activity in certain leukocytes.

GM-CSF & M-CSF

Growth & differentiation factors for leukocyte progenitor cells in bone marrow.

TNF-a, TGF-B, & IL-1

Stimulation of inflammation & fever

IL-12

Growth in T lymphocytes and NK cells

IL-2 & IL-4

Growth factors for T helper cells & B lymphocytes.

IL-5

Eosinophil proliferation, differentiation, & activition

Interferon-y & IL-4

Activation of macrophages

IL-10

Inhibition of macrophages & specific adaptive immune system.

Interferon-a&b

Antiviral activity

IL-8

Chemokine for neutrophils & T lymphocytes

Antigen

Regions of macromolecules, usually proteins that are recognized by lymphocytes to elicit a specific immune response against them.

Antibodies

Are immunoglobulins produced by plasma cells after a progenitor B cell is activated by a specific antigen and rearrange its immunoglobulin genes to antibody that matches the antigen.

Peyer’s Patches

Very large clusters of lymphoid follicles located in the wall of the ileum which allow close monitoring of microorganisms in the gut.

Spleen

Contains the largest single accumulation of lymphoid tissue in the body and is the only lymphoid organ involved in filtration of blood.

• It emerges trabeculae to penetrate the parenchyma or splenic pulp.

Splenic Sinusoids

Are lined by unusual endothelial cells called STAVE CELLS that are elongated and aligned parallel to the blood flow, with open slits between the cells.